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Abstract:

Disclosed is an ultrasound assembly. The ultrasound assembly includes a
garment configured to be affixed to a portion of a living body, and at
least one ultrasound transducer having a fixed position on the garment
and configured to provide at least one of: produce and receive,
ultrasound signals that pass through the living body. The ultrasound
assembly further includes an ultrasound processing unit operatively
associated with the at least one ultrasound transducer and configured to
process the ultrasound signals following passage through the living body,
and an ultrasound-interface unit operatively associated with the
ultrasound processing unit and configured to provide information with
respect to the ultrasound signals following passage through the living
body.

Claims:

1. An ultrasound assembly, comprising: i. a garment configured to be
affixed to a portion of a living body; ii. at least one ultrasound
transducer having a fixed position on said garment and configured to
provide at least one of: a) produce; and b) receive ultrasound signals
that pass through the living body; iii. an ultrasound processing unit
operatively associated with said at least one ultrasound transducer and
configured to process said ultrasound signals following passage through
the living body; and iv. an ultrasound operator-interface unit
operatively associated with said ultrasound processing unit and
configured to provide information with respect to said ultrasound signals
following passage through the living body, wherein said at least one
transducer comprises at least one transducer array.

2. The assembly according to claim 1, including an ultrasound
beam-forming unit configured to produce ultrasound beam propagation
wherein at least one of: i. at least one sub-array; ii. said at least one
array; iii. a plurality of transducer arrays; and iv. said at least one
transducer are configured to provide beams consisting of at least one of:
a. transmitting; and b. receiving, and said ultrasound processing unit
includes a software module configured to process information from said
provided beams.

3. The assembly according to claim 1, including at least one rail
juxtaposed along said garment and at least one of: i. at least one
sub-array; ii. said at least one array; iii. a plurality of transducer
arrays; and iv. said at least one transducer, are configured to move
along said at least one rail.

4. The assembly according to claim 1, including at least one
transducer-locating sensor operatively associated with said ultrasound
processing unit, said at least one transducer-locating sensor occupying
at least one position of: i. on said garment; and ii. at a distance from
said garment, and said ultrasound processing unit includes a software
module configured to process spatial information from said at least one
transducer-locating sensor.

5. The assembly according to claim 2, wherein said system includes at
least one of: i. a plurality of sub-arrays; and ii. said plurality of
transducer arrays, and wherein said ultrasound processing unit includes a
software module configured to compound signals received to produce at
least one output dataset.

7. The assembly according to claim 2, wherein said ultrasound processing
unit includes a software-based compounding module configured to produce
output datasets from input datasets; wherein said input datasets comprise
information from said provided beams; by: i. interpolating data for each
input dataset to a coordinate grid of every output dataset; ii.
calculating a weighted mean over all input datasets per output grid
point, using input datasets whose field of view covers the relevant grid
point.

8. The assembly according to claim 7, wherein the weights for said
weighted mean may be computed according to various criteria, said various
criteria comprising at least one of: i. higher weights are assigned to
input datasets whose nearby pixels provide better lateral resolution; ii.
weights are assigned in inverse proportion to the effective volume of the
relevant pixels within an input dataset; iii. weights are assigned
according to a signal-to-noise ratio estimate per input dataset; and iv.
low weights are assigned to datasets in which the local signal level is
significantly lower than in the other datasets.

9. The assembly according to claim 2, including at least one transducer,
producing different waveforms, wherein said ultrasound processing unit
includes a software module-based process configured to provide various
functions of datasets acquired by said at least one transducer at
different waveforms that are calculated, thereby providing information
with respect to local tissue type.

10. The assembly according to claim 2, wherein said ultrasound processing
unit is configured to receive input datasets acquired from multiple
directions, and, for at least one small target region located in more
than one of said input datasets, apply an elastic registration process to
relevant measurements in said input datasets.

11. The assembly according to claim 10, wherein said ultrasound
processing unit extracts from outputs of said elastic registration
process at least one of: i. local attenuation coefficient measurements;
wherein said elastic registration process is applied to at least two of
said input datasets undergoing cumulative attenuation along different
paths; wherein said cumulative attenuation results from local attenuation
within said living body; and ii. local speed of sound measurements;
wherein said elastic registration process is applied to at least two of
said input datasets undergoing cumulative time delays along different
paths; wherein said cumulative time delays result from local attenuation
within said living body.

12. The assembly according to claim 2, wherein said ultrasound processing
unit includes a software module-based process configured to reduce
clutter effects, comprising: i. acquiring at least one frame of data for
the target volume; and ii. for each sample range-gate at each beam
position calculating a beam pattern for the current range, with respect
to an applicable scanning apex, at all other beam positions; wherein said
beam pattern is normalized so that the peak value is 1.0.

13. The assembly according to claim 12, wherein said software
module-based process is further configured to subtract from said sample
range-gate measurement values at the same range, with respect to said
applicable scanning apex, for a group of other beam positions, where each
measurement value is multiplied by the corresponding said beam pattern
value, and wherein said group of other beam positions comprises beam
positions for which at least one value is high, said high value
comprising at least one of: i. a measurement; and ii. said beam pattern.

14. The assembly according to claim 2, wherein said ultrasound processing
unit includes a software module configured to generate ultrasound
computed tomography or ultrasound diffraction tomography images by
geometrically transforming at least one of: i. scanning processing
parameters; and ii. signal processing parameters; to obtain samples
equivalent to those obtained using at least one of: a. cylindrical
geometry; and b. spherical geometry.

15. The assembly according to claim 1, including at least one
electromagnetic radiation source, said at least one electromagnetic
radiation source occupying at least one position of: i. on said garment;
and ii. at a distance from said garment, and said at least one
electromagnetic radiation source includes at least one of: a. light
source; and b. radio-frequency (RF) source, wherein said ultrasound
processing unit includes a software module-based process configured to
extract from ultrasonic reflections information regarding at least one
of: i. local optical absorption; and ii. local RF absorption.

16. The assembly according to claim 15, wherein said ultrasound
processing unit includes a software module-based process configured to
perform at least one of the following techniques: i. ultrasound computed
tomography; ii. ultrasound computed tomography with geometric
transformation; iii. attenuation correction using local attenuation
coefficient measurements; and iv. time-delay correction using local speed
of sound measurements.

18. The assembly according to claim 2, wherein said ultrasound processing
unit includes a software module-based process configured to receive data
from calibration beams, wherein said calibration beams include at least
one of: i. transmit beams; and ii. receive beams, and said process aligns
said transmit beams and said receive beams.

19. The assembly according to claim 2, wherein multiple strong reflectors
are embedded in known positions along said garment; said strong
reflectors comprising at least one of: i. different shapes; and ii.
different reflection characteristics, and said ultrasound processing unit
includes a software module configured to discriminate between said strong
reflectors.

20. The assembly according to claim 2, wherein an array of high intensity
transducers is integrated into said ultrasound garment and at least one
said high intensity transducer is at least one of: i. dedicated to high
intensity focused ultrasound (HIFU) operation; and ii. dedicated to
imaging purposes, and wherein said ultrasound processing unit includes a
software module configured to utilize at least one of: i. the local
measurements of ultrasound attenuation; and ii. the local measurements of
speed of sound, to adaptively optimize the beam-forming parameters of
said high intensity transducers.

21. The assembly according to claim 1, wherein said garment comprises at
least one apparel comprising at least one of: a belt; a shirt; and a pair
of pants.

Description:

RELATED APPLICATION

[0001] This application claims priority from U.S. Patent Application Ser.
No. 61/056,069 filed 27 May 2008, the content of which is hereby
incorporated by reference as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

[0002] The present invention, in some embodiments thereof, relates to
fixing the position of an ultrasound transducer with respect to a subject
and, more particularly, but not exclusively, to fixing the position of an
ultrasound transducer within a garment affixed to the subject.

[0003] Ultrasound is a well matured medical imaging modality. It provides
two-dimensional (2D) and/or three-dimensional (3D) anatomic information
as well as a plurality of physiological and functional parameters at
relatively high refresh rates, reaching an order of 100 frames per second
for 2D imaging.

[0004] The imaging platforms are portable and reasonably priced. However,
ultrasound imaging suffers from some disadvantages, chief of which are
low image quality compared to other imaging modalities, for example
Computed Tomography (CT) and Magnetic Resonance Imaging (MRI); and
limited volume coverage.

[0005] Conventional phased array transducers have a limited field of view
due to limitations at the beam steering end, i.e., due to off-broadside
beam widening; the effective area of planar transducers decreases with
the off-broadside angle, thus increasing the beam width.

[0006] The maximal beam penetration depth is also limited by signal
attenuation within the tissue. Decreasing the transmission frequency
reduces the attenuation and increases the penetration depth, but also
worsens the spatial resolution.

[0007] One of the methods known in the art for addressing these issues is
image registration and compounding. The term `registration` relates to
the process of finding a transformation that maps each point in one image
or coordinate system to corresponding points in another image or
coordinate system. The term `compounding` relates to the combination of
data from multiple registered images to produce one or more registered
images.

[0008] The registration process may either be algorithm based, or sensor
based.

[0009] In algorithm based registration, the sole input is a set of
reconstructed imaging planes or volumes. For example as described by
Foroughi P, Abolmaesumi P, Hashtrudi-Zaad K; "Intra-Subject Elastic
Registration of 3D Ultrasound Images"; Medical Image Analysis 2006;
10:713-725.

[0010] In sensor based registration, data acquired by positioning and/or
orientating sensors is also utilized. For example as taught in US Patent
Application 2007/0081709; Apr. 12, 2007 by Warmath R J, Herline A J;
"Method and Apparatus for Standardizing Ultrasonography Training Using
Image to Physical Space Registration of Tomographic Volumes from Tracked
Ultrasound".

[0011] The documented advantages and features of ultrasound image
registration and compounding include, for instance:

[0014] iii. Speckle noise reduction. Speckle is a result of the fact that
the reflecting particles within tissues are much smaller than the
wavelength used. The effect of speckle may be modeled as multiplicative
noise. Speckle patterns are very sensitive to small changes in the
relative location of the transducer and the tissue volume, and can be
reduced by local averaging over several frames, taken at different times
or probe positions/orientations. For example as described by Krucker J F,
Meyer C R, LeCarpentier G L, Fowlkes J B, Carson P L; "3D Spatial
Compounding of Ultrasound Images Using Image-Based Nonrigid
Registration"; Ultrasound in Medicine and Biology 2000; 26:1475-1488.

[0015] iv. Minimization of shadowing artifacts. Shadowing is caused by
tissues along the ultrasonic beam that have a high reflection and/or
attenuation coefficient, so that the ultrasound energy reaching tissues
further away from the transducer (along the ultrasonic beam) is
significantly reduced. This differently affects ultrasound images
acquired from different angles, and can therefore be mitigated by spatial
compounding. For example, as described by Krucker J F, Meyer C R,
LeCarpentier G L, Fowlkes J B, Carson P L; "3D Spatial Compounding Of
Ultrasound Images Using Image-Based Nonrigid Registration"; Ultrasound in
Medicine and Biology 2000; 26:1475-1488.

[0017] vi.
Estimation of speed of sound factors within different tissues, using time
delays measured at different directions; for example as taught in US
Patent Application 2007/0167757; Jul. 19, 2007; Haimerl M; "Determining
Speed-of-Sound Factors in Ultrasound Images of a Body".

[0018] vii.
Change estimation and regional motion evaluation, utilizing 2D or 3D
imaging information acquired for the same tissue volume at several
timeframes. In some cases, the registration may be performed globally,
but local registration is usually required, tracking the location change
over time for every small region, for example as described by optic-flow
techniques. If the time difference between consecutive images is
relatively short, applying cross-correlation functions to the local
speckle pattern can allow accurate regional motion assessment. For
example as taught in U.S. Pat. No. 5,876,342; Mar. 2, 1999; Chen J F,
Weng L; "System and Method for 3-D Ultrasound Imaging and Motion
Estimation".

[0019] viii. Angle independent Doppler measurement. Standard
ultrasound systems estimate flow velocity, for example blood flow
velocity, using the Doppler Effect, which only provides information
regarding the radial component of the velocity vector. When multiple
receiving transducers are employed, placed at different angular locations
with respect to the target volume, one can estimate the magnitude and
orientation of the flow velocity vector. For example as taught in U.S.
Pat. No. 5,409,010; Apr. 25, 1995; Beach K, Overbeck J; "Vector Doppler
Medical Devices For Blood Velocity Studies".

[0021] Some state-of-the-art 3D imaging probes with improved field of view
have also been suggested, for instance:

[0022] i. As taught in
International Patent Application WO2004/001447; Dec. 31, 2003; Poland and
Sumanaweera et al.; "System and Method for Electronically Altering
Ultrasound Scan Line Origin for a Three-Dimensional Ultrasound System";
and as taught in US Patent Application 2006/0078196; Apr. 13, 2006;
Sumanaweera T S, Cai A H, Ustuner K F; "Distributed Apexes for 3-D
Ultrasound Scan Geometry"; which describe 2D or multi-dimensional (MD)
phased arrays which can adaptively generate scan lines apparently
emanating from a location ("apex") other than the geometric center of the
transducer probe. Multiple apexes may be generated, allowing the
optimization of the scanned volume to the transducer's characteristics.

[0023] ii. As taught in US Patent Application 2006/0173333; Aug. 3, 2006;
Sudol W.; "Two-Dimensional Transducer Arrays for Improved Field of View";
where a similar concept is presented, wherein different groups of
adjacent rows and/or columns of transmitting and/or receiving transducer
components are activated at different times. Sudol also suggests the
possibility of using a convex 2D array, as well as using two or more
probes concurrently.

[0024] iii. As taught in US Patent Application
2007/0066902; Mar. 22, 2007; Wilser and Mohr; "Expandable Ultrasound
Transducer Array"; describing a foldable transducer array, intended to be
used within the subject's body. While folded, the transducer array has a
smaller width or volume, for insertion into and withdrawal from, for
example a hollow region within the subject. When unfolded, foldable
transducer array provides a larger radiation surface.

[0025] Another system and technique, which effectively improves image
quality and increases image volume, is ultrasound computed tomography
(UCT). UCT is founded on inverse problem concepts, similar to those used
for X-ray CT. UCT has two basic implementations:

[0026] i. Reflection
mode: In this case, the source, for example the transmitting array, and
the detector, for example the receiving array; are on the same side of
the subject or the target region. The transmitting array and the detector
are rotated about a certain rotation axis, and in some cases also
translated along that axis. In each geometric configuration, a short
ultrasound pulse is transmitted, and the reflected echoes, resulting from
discontinuities in the speed of sound within the medium, are measured as
a function of time, which corresponds to the distance between the
reflector and the transducer; for example as taught in US Patent
Application 2006/0106307; May 18, 2006; Dione D P, Staib L H, Smith W;
"Three-Dimensional Ultrasound Computed Tomography Imaging System".

[0027]
ii. Transmission mode: In this configuration, the source and the detector
are placed on opposite sides of the subject or the target region, and are
rotated and/or translated together; for example as taught in U.S. Pat.
No. 4,509,368; Apr. 9, 1985; Whiting J F, Koch R H L; "Ultrasound
Tomography". For each beam, the time difference between the transmission
of the pulse and its detection on the other side; for example as
described by using rise-time detection or threshold detection on receive;
provides information regarding the overall time of flight, which is
inversely proportional to the average speed of sound along the beam. The
power ratio between the transmitted pulse and the received pulse provides
an estimate of the total signal attenuation along the beam.

[0028] In some cases, multiple sources and/or detectors are used to reduce
the overall scanning time.

[0029] Both UCT modes use circular or helical scanning of the subject. A
slightly different geometry has been suggested by Li P C, Huang S W;
"Ultrasound Tomography of the Breast Using Linear Arrays"; ICASSP 2005;
V-989-V-992; who compressed a female breast between a linear transducer
array and a reflective metal plate. Separate groups of transducer
components are allocated for signal transmission and reception. The
relative location of the selected groups with respect to the metal plate
determines the path of the ultrasonic beam.

[0030] A variation of UCT, called ultrasound diffraction tomography (UDT),
is based on measuring the forward scattered ultrasound field as a
function of cross-range with respect to the incident wave. This technique
also requires the utilization of more complex reconstruction methods; for
example as described by Louis A K; "Medical Imaging: State of the Art and
Future Development"; Inverse Problems 1992; 8:709-738.

[0031] Furthermore, ultrasound imaging has the potential to expand its
clinical applications beyond its presently prevalent capabilities, and
also provide tissue classification parameters. Elastography has been
proposed as a way to achieve this goal; for example as described by
Melodelima D, Bamber J C, Duck F A, Shipley J A, Xu L; "Elastography for
Breast Cancer Diagnosis using Radiation Force: System Development and
Performance Evaluation"; Ultrasound in Medicine and Biology 2006;
32:387-396. The term elastography encompasses a variety of techniques
that can depict a mechanical response or property of tissues. In
ultrasound, the elastography premise is built on two known facts:

[0032] i. There are significant differences between mechanical properties
of several tissue components.

[0033] ii. The time-dependent information
contained in the measured speckle patterns is sufficient to depict these
differences following an external or internal mechanical stimulus. This
stimulus may be generated, for example by applying an external pressure
to the skin surface, or by vibrating a region at a low frequency.

[0034] Ultrasound also has therapeutic applications, using high intensity
focused ultrasound (HIFU) technologies, which increase the local
temperature at a region near the focal point of a high energy ultrasound
transducer, thus causing local tissue ablation; for example as taught in
US Patent Application 2008/0051656; Feb. 28, 2008; Vaezy S, Chan A N,
Fujimoto V Y, Moore D E, Martin R W; "Method for Using High Intensity
Focused Ultrasound".

SUMMARY OF THE INVENTION

[0035] According to an aspect of some embodiments of the invention, there
is provided an ultrasound assembly. The ultrasound assembly includes a
garment configured to be affixed to a portion of a living body, and at
least one ultrasound transducer having a fixed position on the garment
and configured to provide at least one of: produce and receive ultrasound
signals that pass through the living body. The ultrasound assembly
further includes an ultrasound processing unit operatively associated
with the at least one ultrasound transducer and configured to process the
ultrasound signals following passage through the living body, and an
ultrasound operator-interface unit operatively associated with the
ultrasound processing unit and configured to provide information with
respect to the ultrasound signals following passage through the living
body.

[0036] In some embodiments of the invention, the garment is configured to
cover at least a portion of a body part of the living body including at
least one of: an abdomen, a torso, a pelvis, an arm, a foot, and a head.

[0037] In some embodiments of the invention, the garment comprises at
least one apparel including at least one of: a belt, a shirt, and a pair
of pants.

[0038] In some embodiments of the invention, the garment is comprised of
at least two parts, separated by at least one band, the at least one band
being at least one of: relatively stretchable, and relatively
unstretchable.

[0039] In some embodiments of the invention, the garment has an open
configuration which may be adjustably closed around at least a portion of
a body part and includes a closure including at least one of: Velcro,
straps, tape, and clips.

[0040] In some embodiments of the invention, the garment includes an inner
surface and an outer surface and includes, to keep the garment in place,
at least one of: sticky patches on the inner surface, vacuum chambers on
the inner surface, and pressure chambers on the outer surface.

[0041] In some embodiments of the invention, the garment includes at least
one fixation point to which the at least one transducer removably
attaches.

[0042] In some embodiments of the invention, the garment is configured to
receive at least one mechanical fixture operatively associated with the
at least one transducer, the mechanical fixture configured to maintain
the at least one transducer affixed to the garment.

[0043] In some embodiments of the invention, the at least one transducer
comprises at least one transducer array.

[0044] In some embodiments of the invention, the at least one transducer
array comprises a plurality of transducer arrays.

[0045] In some embodiments of the invention, the plurality of transducer
arrays are spaced with respect to each other according to at least one
of: a distance, and in close proximity.

[0046] In some embodiments of the invention, the at least one transducer
array is configured in at least one of: a one-dimensional array (1D), a
two dimensional array (2D), and a multi-dimensional (MD) grid pattern.

[0047] In some embodiments of the invention, the at least one transducer
array comprises a grid pattern including at least one of: Cartesian and
hexagonal patterns.

[0048] In some embodiments of the invention, the at least one transducer
array comprises a sparse grid.

[0049] In some embodiments of the invention, the at least one transducer
array includes at least one sub-array.

[0050] In some embodiments of the invention, the assembly includes an
ultrasound beam-forming unit configured to produce ultrasound beam
propagation wherein at least one of: at least one sub-array, the at least
one array, a plurality of transducer arrays, and the at least one
transducer are configured to provide beams consisting of at least one of:
transmitting, and receiving, and the ultrasound processing unit includes
a software module configured to process information from the provided
beams.

[0051] In some embodiments of the invention, the ultrasound beam-forming
unit is configured to produce ultrasound beam propagation in at least one
of: two-way, and one-way, through the living body.

[0052] In some embodiments of the invention, the at least one transducer
array includes at least one acoustic lens covering at least a portion of
one of: at least one sub-array, the at least one array, a plurality of
transducer arrays, and the at least one transducer.

[0053] In some embodiments of the invention, at least one of: at least one
sub-array, the at least one array, a plurality of transducer arrays, and
the at least one transducer, are configured to scan at least one of: a
surface, and a volume.

[0054] In some embodiments of the invention, at least one of: at least one
sub-array, the at least one array, a plurality of transducer arrays, and
the at least one transducer, are configured to scan using at least one
of: electronic scanning, and mechanical scanning.

[0055] In some embodiments of the invention, the mechanical scanning is
performed by at least one of: swinging, rotating, and oscillating.

[0056] In some embodiments of the invention, the assembly includes at
least one rail juxtaposed along the garment and at least one of: at least
one sub-array, the at least one array, a plurality of transducer arrays,
and the at least one transducer, are configured to move along the at
least one rail.

[0057] In some embodiments of the invention, the movement is induced by at
least one movement of: manual, and motorized.

[0058] In some embodiments of the invention, the at least one rail
includes cogs operatively associated with at least one motor having at
least one cog wheel configured to cause the movement along the at least
one rail.

[0059] In some embodiments of the invention, the assembly includes at
least one transducer-locating sensor operatively associated with the
ultrasound processing unit, the at least one transducer-locating sensor
occupying at least one position of: on the garment, and at a distance
from the garment, and the ultrasound processing unit includes a software
module configured to process spatial information from the at least one
transducer-locating sensor.

[0060] In some embodiments of the invention, the at least one
transducer-locating sensor comprises at least three transducer-locating
sensors a distance from the garment and the ultrasound processing unit is
configured to provide spatial triangulation of various points along the
garment from the at least three transducer-locating sensors.

[0061] In some embodiments of the invention, the at least one
transducer-locating sensor comprises at least one video camera configured
to record location of various points along the garment.

[0062] In some embodiments of the invention, the at least one
transducer-locating sensor occupying at least one position on the garment
comprises at least one of: a magnetic sensor, an electro-magnetic sensor,
and a radio frequency identification (RFID).

[0063] In some embodiments of the invention, the garment includes at least
one fold that includes at least one of: an electronic sensor, and a
mechanical sensor, configured to measure spatial angles along the at
least one fold and transmit the spatial angles to the ultrasound
processing unit.

[0064] In some embodiments of the invention, the ultrasound processing
unit additionally includes a software module configured to process the
spatial angles for at least one of: at least one sub-array, the at least
one array, a plurality of transducer arrays, and the at least one
transducer, located on each side of the one fold.

[0065] In some embodiments of the invention, the at least one transducer
comprises one large ultrasonic array system and the ultrasound processing
unit includes a software module configured to receive data and process
data from the one large ultrasonic array system.

[0066] In some embodiments of the invention, the beam-forming unit is at
least one of: included in the garment, and located a distance from the
garment.

[0067] In some embodiments of the invention, the at least one ultrasound
transducer comprises an "active" phased array which supports the
generation of multiple receive beams in post ultrasound-receiving
processing.

[0068] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to operate the "active" phased
array.

[0069] In some embodiments of the invention, the ultrasound beam-forming
unit is configured to support at least one imaging mode including at
least one of: reflection-based volume imaging, reflection-based
ultrasound computed tomography (UCT), reflection-based ultrasound
diffraction tomography (UDT), reflection-based beam pairs,
transmission-based UCT, and transmission-based UDT.

[0070] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to operate the ultrasound
beam-forming unit such that the ultrasound processing unit receives and
processes at least one mode including at least one of: transmitting, and
receiving at least one beam concurrently.

[0071] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to receive and process at
least one dataset of: 1D, 2D, and 3D.

[0072] In some embodiments of the invention, the receiving comprises at
least one of: time-dependent, and time-independent.

[0073] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to receive and process
repetitive scans of at least one of: a plane, and a volume, at predefined
angular directions.

[0074] In some embodiments of the invention, the system includes at least
one of: a plurality of sub-arrays, and the plurality of transducer
arrays, and wherein the ultrasound processing unit includes a software
module configured to compound signals received to produce at least one
output dataset.

[0075] In some embodiments of the invention, the at least one dataset
comprises at least two datasets which are combined, thereby achieving at
least one of: extending a field of view, reducing speckle noise,
improving signal-to-noise ratio, reducing shadowing artifacts, reducing
clutter artifacts, enhancing spatial resolution, and enhancing image
contrast.

[0076] In some embodiments of the invention, the at least two datasets are
combined according to a predefined logic.

[0077] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to provide computed tomography
imaging and using a data analysis system based upon obtaining
measurements using at least one of: cylindrical geometry, and spherical
geometry.

[0078] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to compare
reflections measured using opposite collinear beams to yield estimates of
at least one of: a local attenuation coefficient, and a local speed of
sound.

[0079] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to receive data
from calibration beams, wherein the calibration beams include at least
one of: transmit beams, and receive beams, and the process aligns the
transmit beams and the receive beams.

[0080] In some embodiments of the invention, multiple strong reflectors
are embedded in known positions along the garment, the strong reflectors
including at least one of: different shapes, and different reflection
characteristics, and the ultrasound processing unit includes a software
module configured to discriminate between the strong reflectors.

[0081] In some embodiments of the invention, the ultrasound processing
unit includes a software registration module configured to receive data
which is one of: ultrasonic image based, sensor based, and ultrasonic
image and sensor based.

[0082] In some embodiments of the invention, the ultrasound processing
unit includes a software-based compounding module configured to produce
output datasets from input datasets, wherein the input datasets comprise
information from the provided beams, by: interpolating data for each
input dataset to a coordinate grid of every output dataset, calculating a
weighted mean over all input datasets per output grid point, using input
datasets whose field of view covers the relevant grid point.

[0083] In some embodiments of the invention, interpolation is performed
simultaneously to all input datasets.

[0084] In some embodiments of the invention, the weights for the weighted
mean may be computed according to various criteria, the various criteria
including at least one of: higher weights are assigned to input datasets
whose nearby pixels provide better lateral resolution, weights are
assigned in inverse proportion to the effective volume of the relevant
pixels within an input dataset, weights are assigned according to a
signal-to-noise ratio estimate per input dataset, and low weights are
assigned to datasets in which the local signal level is significantly
lower than in the other datasets.

[0085] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to provide at
least one of: averaging, and weighted averaging, which are assigned to
multiple datasets of several waveforms to reduce clutter effects.

[0086] In some embodiments of the invention, the assembly includes at
least one transducer, producing different waveforms, wherein the
ultrasound processing unit includes a software module-based process
configured to provide various functions of datasets acquired by the at
least one transducer at different waveforms that are calculated, thereby
providing information with respect to local tissue type.

[0087] In some embodiments of the invention, statistical attributes of the
waveform dependent data are utilized, the statistical attributes
including at least one of: average, weighted average, standard deviation,
and maximum to minimum ratio.

[0088] In some embodiments of the invention, the ultrasound processing
unit is configured to receive input datasets acquired from multiple
directions, and, for at least one small target region located in more
than one of the input datasets, apply an elastic registration process to
relevant measurements in the input datasets.

[0089] In some embodiments of the invention, the ultrasound processing
unit extracts local attenuation coefficient measurements from outputs of
the elastic registration process, wherein the elastic registration
process is applied to at least two of the input datasets undergoing
cumulative attenuation along different paths, wherein the cumulative
attenuation results from local attenuation within the living body.

[0090] In some embodiments of the invention, the ultrasound processing
unit extracts local speed of sound measurements from outputs of the
elastic registration process, wherein the elastic registration process is
applied to at least two of the input datasets undergoing cumulative time
delays along different paths, wherein the cumulative time delays result
from local attenuation within the living body.

[0091] In some embodiments of the invention, the elastic registration is
performed on at least one of: pairs of opposite collinear beams, and
groups of adjacent opposite collinear beams.

[0092] In some embodiments of the invention, in the pairs of opposite
collinear beams, the registration is reduced to a single dimension and
searching is done for specific patterns, including at least one of:
maxima, minima, and other predefined patterns.

[0093] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to reduce
clutter effects, including: acquiring at least one frame of data for the
target volume, and for each sample range-gate at each beam position
calculating a beam pattern for the current range, with respect to an
applicable scanning apex, at all other beam positions, wherein the beam
pattern is normalized so that the peak value is 1.0.

[0094] In some embodiments of the invention, the software module-based
process is further configured to subtract from the sample range-gate
measurement values at the same range, with respect to the applicable
scanning apex, for all other beam positions, where each measurement value
is multiplied by the corresponding beam pattern value.

[0095] In some embodiments of the invention, the software module-based
process is further configured to subtract from the sample range-gate
measurement values at the same range, with respect to the applicable
scanning apex, for a group of other beam positions, where each
measurement value is multiplied by the corresponding beam pattern value,
and wherein the group of other beam positions comprises beam positions
for which at least one value is high, the high value including at least
one of: a measurement, and the beam pattern.

[0096] In some embodiments of the invention, the software module-based
process performs iterative processing until a cessation criterion has
been met.

[0097] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to utilize data from at least
one of: the at least one sub-array, the at least one array, the plurality
of transducer arrays, and the at least one transducer, to provide
pulsed-wave (PW) Doppler studies, wherein a full spectrum for a specific
region is acquired from multiple directions, thus extending the
information provided.

[0098] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to utilize data from at least
one of: the at least one sub-array, the at least one array, the plurality
of transducer arrays, and the at least one transducer, to provide
continuous-wave (CW) Doppler studies, wherein at least two intersecting
beams, whose boresight directions over time may be at least one of:
constant, and changing, are utilized to extract spatially dependent data.

[0099] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to use Doppler shift
measurements from at least two points of view and reconstruct a 2D
projection of a 3D velocity vector corresponding to the dominant velocity
for at least one pixel.

[0100] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to receive Doppler shift
measurements from at least three points of view and reconstruct a full 3D
velocity vector for at least one pixel.

[0101] In some embodiments of the invention, an array of high intensity
transducers is integrated into the ultrasound garment and at least one
the high intensity transducer is at least one of: dedicated to high
intensity focused ultrasound (HIFU) operation, and dedicated to imaging
purposes.

[0102] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to utilize at least one of:
the local measurements of ultrasound attenuation, and the local
measurements of speed of sound, to adaptively optimize the beam-forming
parameters of the high intensity transducers.

[0103] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to generate ultrasound
computed tomography or ultrasound diffraction tomography images by
geometrically transforming at least one of: scanning processing
parameters, and signal processing parameters, to obtain samples
equivalent to those obtained using at least one of: cylindrical geometry,
and spherical geometry.

[0104] In some embodiments of the invention, geometric transformation
includes introducing at least one equation of: phase delays, and time
delays, to each transducer component, wherein the at least one equation
refers to at least one of: transmission, and reception.

[0105] In some embodiments of the invention, the assembly includes at
least one electromagnetic radiation source, the at least one
electromagnetic radiation source occupying at least one position of: on
the garment, and at a distance from the garment, and the at least one
electromagnetic radiation source includes at least one of: light source,
and radio-frequency (RF) source.

[0106] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to extract from
ultrasonic reflections information regarding at least one of: local
optical absorption, and local RF absorption.

[0107] In some embodiments of the invention, the ultrasound processing
unit includes a software module-based process configured to perform at
least one of the following techniques: ultrasound computed tomography,
ultrasound computed tomography with the geometric transformation,
attenuation correction using the local attenuation coefficient
measurements, and time-delay correction using the local speed of sound
measurements.

[0108] According to another aspect of some embodiments of the invention,
there is provided, an ultrasound assembly, including: at least one
ultrasound transducer array configured to be placed against a living
body, an ultrasound beam-forming unit operatively associated with the at
least one ultrasound transducer array, the ultrasound beam-forming unit
configured to cause the at least one ultrasound transducer array to
produce and receive at least one pair of opposite collinear beams that
pass through the living body, an ultrasound processing unit operatively
associated with the ultrasound beam-forming unit and configured to
receive and compare the at least one pair of opposite collinear beams to
yield estimates of at least one of: a local attenuation coefficient, and
a local speed of sound.

[0109] In some embodiments of the invention, the ultrasound processing
unit is configured to apply an elastic registration process to relevant
measurements of the at least one pair of opposite collinear beams, and
for each pair of opposite collinear beams perform at least one of:
extract local attenuation coefficient measurements from outputs of the
elastic registration process, wherein the pair of opposite collinear
beams, to which the elastic registration is applied, undergoes cumulative
attenuation along opposite beam paths, wherein the cumulative attenuation
results from local attenuation within the living body, and extract local
speed of sound measurements from outputs of the elastic registration
process, wherein the pair of opposite collinear beams, to which the
elastic registration is applied, undergoes cumulative time delays along
opposite beam paths, wherein the cumulative time delays result from local
variations in speed of sound within the living body.

[0110] In some embodiments of the invention, in pairs of opposite
collinear beams, the registration is reduced to a single dimension and
searching for specific patterns, including at least one of: maxima,
minima, and other predefined patterns.

[0111] According to still another aspect of some embodiments of the
invention, there is provided, an ultrasound assembly, including: at least
one ultrasound transducer array configured to be placed against a living
body, an ultrasound beam-forming unit operatively associated with the at
least one ultrasound transducer array and configured to cause the at
least one ultrasound transducer array to produce and receive multiple
ultrasound signals through multiple small target regions in the living
body, an ultrasound processing unit operatively associated with the
ultrasound beam-forming unit and configured to compare the multiple
ultrasound signals for each of the multiple small target regions to yield
estimates of at least one of: a local attenuation coefficient, and a
local speed of sound.

[0112] In some embodiments of the invention, the ultrasound processing
unit includes a software module configured to apply an elastic
registration process to the multiple ultrasound signals, and perform at
least one of: extract local attenuation coefficient measurements from
outputs of the elastic registration process, wherein the multiple
ultrasound signals, to which the elastic registration is applied, undergo
cumulative attenuation along different paths, wherein the cumulative
attenuation results from local attenuation within the living body, and
extract local speed of sound measurements from outputs of the elastic
registration process, wherein the multiple ultrasound signals, to which
the elastic registration is applied, undergo cumulative time delays along
different paths, wherein the cumulative time delays result from local
variations in speed of sound within the living body.

[0113] In some embodiments of the invention, the extraction is repeated
for the multiple small target regions to provide a sound map of at least
one region, including at least one of: a 2D region, and a 3D region.

[0114] In some embodiments of the invention, the extraction is repeated
for the multiple small target regions to provide a 3D sound map and the
software module is configured to: divide an output grid into layers taken
at incremental ranges, determine a spatial map of at least one of:
attenuation coefficients, and speeds of sound, and produce and correct a
reflection coefficient map.

[0115] In some embodiments of the invention, the software module is
additionally configured to produce and combine at least two of the
following maps: reflection coefficients, attenuation coefficients, and
speeds of sound, and provide tissue type classification data.

[0116] Unless otherwise defined, all technical and/or scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the invention pertains. Although
methods and materials similar or equivalent to those described herein can
be used in the practice or testing of embodiments of the invention,
methods and/or materials are described below. In case of conflict, the
patent specification, including definitions, will control. In addition,
the materials, methods, and examples are illustrative only and are not
intended to be necessarily limiting.

[0117] Implementation of the method and/or system of embodiments of the
invention can involve performing or completing selected tasks manually,
automatically, or a combination thereof. Moreover, according to actual
instrumentation and equipment of embodiments of the method and/or system
of the invention, several selected tasks could be implemented by
hardware, software, or firmware; or by a combination thereof using an
operating system.

[0118] For example, hardware for performing selected tasks according to
embodiments of the invention could be implemented as a chip or a circuit.
As software, selected tasks according to embodiments of the invention
could be implemented as a plurality of software instructions being
executed by a computer using any suitable operating system.

[0119] In embodiments of the invention, one or more tasks according to
embodiments of method and/or system as described herein are performed by
a data processor, such as a computing platform for executing a plurality
of instructions. Optionally, the data processor includes a volatile
memory for storing instructions and/or data and/or a non-volatile
storage, for example, a magnetic hard-disk and/or removable media, for
storing instructions and/or data. Optionally, a network connection is
provided as well. A display and/or an operator input device such as a
keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

[0120] Some embodiments of the invention are herein described, by way of
example only, with reference to the accompanying drawings. With specific
reference now to the drawings in detail, it is stressed that the
particulars shown are by way of example and for purposes of illustrative
discussion of embodiments of the invention. In this regard, the
description taken with the drawings makes apparent to those skilled in
the art how embodiments of the invention may be practiced.

[0121] In the drawings:

[0122] FIGS. 1A-1B show representations of an ultrasound system and
operational flow chart, respectively, according to some embodiments of
the invention;

[0123] FIG. 2 shows a single large ultrasonic array system, according to
some embodiments of the invention;

[0124]FIG. 3 shows details of a portion of FIG. 2, according to some
embodiments of the invention;

[0125]FIG. 4 shows an active phased array system, according to some
embodiments of the invention;

[0126] FIG. 5 shows a single sub-array system, according to some
embodiments of the invention. In some configurations, the ultrasound
system may include a plurality of such sub-arrays;

[0127]FIG. 6 shows active phased array systems, according to some
embodiments of the invention;

[0128]FIG. 7 shows effective transducer geometry translation, according
to some embodiments of the invention; and

[0129]FIG. 8 shows graphs of peak location in collinear beam
configurations, according to some embodiments of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0130] The present invention, in some embodiments thereof, relates to
fixing the position of an ultrasound transducer with respect to a subject
and, more particularly, but not exclusively, to fixing the position of an
ultrasound transducer within a garment affixed to the subject.

[0131] Before explaining at least one embodiment of the invention in
detail, it is to be understood that the invention is not necessarily
limited in its application to the details of construction and the
arrangement of the components and/or methods set forth in the following
description and/or illustrated in the drawings and/or the examples. The
invention is capable of other embodiments or of being practiced or
carried out in various ways.

[0132] Referring now to the drawings:

Ultrasonic Imaging System

[0133] In FIGS. 2-6, triangles stand for amplifiers or attenuators and
crossed-out circles stand for phase shifters and/or true time-delay
components. `S.A.` stands for `Sub-Array`, `Sig. Gen.` stands for `Signal
Generator`, and Cij is the j'th channel of sub-array i. When
two or more lines intersect, connections are denoted by small black
singular dots.

[0134] Triplets of black circle symbols without numbers represent copies
of the units appearing in conjunction with the symbols, for example above
and below the symbols.

[0135] FIGS. 1A-1B show representations of an ultrasound (US) system 100
and operational flow chart 104 respectively which includes an ultrasound
garment 110 affixed to a subject 102 and an ultrasound imager 112. While
subject 102 is depicted as a human being, the present invention may be
used and/or configured for use on non-human animals.

[0136] Ultrasound garment 110 includes transducers 124, alternatively
referred to as transducer components 124, fixed in position in ultrasound
garment 110 which, itself, is fixed in position with respect to subject
102.

[0138] The inventor has discovered that transducers 124 having relatively
known location and orientation may provide specific information that can
contribute to the quality of the reconstructed images, for example on
imager 112, as will be explained below.

[0139] US system 100 optionally includes a beam-forming unit 120; a
processing unit 122 and an operator-interface unit 114, alternatively
referred to as user-interface unit 114. In FIG. 1B, data lines are shown
as one-directional arrows. Control/status lines are shown as
two-directional arrows. Dashed lines relate to information which is
optionally present in some embodiments of system 100.

[0141] The ultrasonic signal emanating from reflections and/or
transmission through the body of subject 102 is then sensed by
transducers 124 in ultrasound garment 110; which translate it into an
electronic signal that is sampled by beam-forming unit 120.

[0142] The digitized information is then processed by processing unit 122.
In embodiments, processing unit 122 also receives location and/or
orientation information from ultrasound garment 110. Operator-interface
unit 114 controls beam-forming unit 120; a processing unit 122, and also
displays information to the operator on imager 112. In some embodiments,
said control of operator-interface unit 114 may be performed through
processing unit 122. Certain hardware configurations might combine
ultrasound garment 110 and beam-forming unit 120 into a front-end unit.

[0145] In further embodiments, beam-forming unit 120 provides one or more
driving signals for each array of transducers 124 or sub-array of
transducers 124, as well as a set of parameters controlling the signal
attenuation and/or time-delay for each transducer 124 or group of
transducers. In the latter case, the signal attenuation and/or
time-delays, required for forming the beams, are managed by ultrasound
garment 110.

[0146] As used herein, the term "array" refers to an array
of transducers 124; while the term "sub-array" refers to a sub-array of
transducers 124 located within a larger array.

[0147] ii. Sampling the
electronic signal produced by receiving ultrasonic transducers 124.
Diverse signal types are sampled in different hardware configurations. In
some cases, the signal reaching each transducer 124 or group of
transducers 124 may be sampled. In other cases, one or more linear
functions of some or all of transducers 124 in an array or sub-array may
be measured. The linear combination may be performed by either ultrasound
garment 110 or beam-forming unit 120. The linear weights for this linear
combination can be predefined or calculated, and may be determined by
beam-forming unit 120, by ultrasound garment 110 based on inputs from
beam-forming unit 120, or by ultrasound garment 110 alone. Additionally
or alternatively, the linear weights for the linear combination can be
calculated by processing unit 122.

Garment Variations

[0148] There are a large number of designs and configuration of ultrasound
garment 110. One ultrasound garment 110 embodiment, for example, is
configured to partially or fully cover a certain body part, such as the
abdomen or torso of subject 102.

[0149] Further, ultrasound garment 110 may be alternatively configured
with different shapes; each configured to cover a different portion of a
subject; for example a pelvis, arm, foot, and/or a head.

[0150] Additionally, ultrasound garment 110 optionally is configured to
cover multiple body parts, or even the entire body of a subject. The many
configurations possible for ultrasound garments 110 are easily recognized
and appreciated by those familiar with the art of imaging.

[0151] In embodiments, ultrasound garment 110 is integrated into apparel,
for example a belt, a shirt, or a pair of pants.

[0152] Additionally or alternatively, ultrasound garment 110 optionally
includes two or more parts, allowing more than one possible assembly
configuration, for example by separating one or more bands making up
ultrasound garment 110 prior to fixing the transducers in place.

[0153] Optionally, the surface of ultrasound garment 110 is continuous and
configured to be easily molded to a given body part, for example as an
inflatable cuff around the arm.

[0154] Alternatively ultrasound garment 110 optionally includes some
discontinuities. Additionally or alternatively, the surface of ultrasound
garment 110 includes stretchable "seams" which can be stretched prior to
fixation of the transducer positions.

[0155] In embodiments, ultrasound garment 110 optionally has an open
configuration which may be adjustably closed around a body part. For
example ultrasound garment 110 optionally includes a belt having
adjustable diameter, with a closure system comprising Velcro material
interposed between the belt surfaces. Additional closure systems
optionally include straps, tape, or clips.

[0156] In embodiments, ultrasound garment 110 optionally includes
ultrasound media designed for acoustic impedance matching between
transducers 124 and the body surface of subject 102. Such ultrasound
media optionally, for example, include gel packs, covering parts of, or
the entire inner surface of the apparatus. The gel packs optionally are
disposable or refillable. The media used for acoustic impedance matching
optionally includes a gel. Additionally or alternatively, the media
optionally includes a gas, liquid, or solid.

Garment Fixation

[0157] In embodiments, one or more fixation devices, such as straps,
sticky patches or vacuum patches, optionally are used for keeping
ultrasound garment 110 affixed in place.

[0158] In other embodiments, the fixation device is a part of transducers
124. For example, sticky surfaces or vacuum generating surfaces
optionally are used to maintain transducers in fixed positions.

[0159] Another option for maintaining position of transducers 124 is the
addition of a gas pocket providing negative pressure between the US
transducer array and the body surface, for example, along the inner
surface of the apparatus. The pressure within such a gas pocket
optionally is adjusted to obtain a tighter or a looser fit of ultrasound
garment 110.

[0160] In embodiments, the gas pocket is located along the outer surface
of the apparatus and positive pressure, for example through inflation of
the gas pocket, causes the transducers to be fixed in place.

Transducer Configuration

[0161] In some embodiments, ultrasound garment 110 optionally includes a
large US transducer array; which may be divided into multiple sub-arrays.
Such sub-arrays optionally overlap each other in some configurations,
while in other configurations the sub-arrays are separate. In either
case, the sub-arrays activation can be predefined or adaptively allocated
by the imaging system.

[0165] Optionally, in embodiments, pluralities of transducer arrays are
used. The arrays optionally are placed in close proximity to one another.
Alternatively, the pluralities of transducer arrays optionally are placed
at a distance from each other.

[0166] In some embodiments, each of the multiple arrays has a separate
casing or housing, and even a separate driving unit. In other
embodiments, several arrays are housed together.

[0167] Irrespective of the number of arrays or sub-arrays, each array or
sub-array optionally includes one or more transmitting and/or receiving
transducer components 124, ordered in a one-dimensional (1D),
two-dimensional (2D), or multi-dimensional (MD) grid; wherein the grid
pattern is Cartesian.

[0168] Alternatively, the grid pattern has a different pattern, for
example, one or more hexagonal patterns. In still further embodiments,
sparse grids are utilized. In some embodiments, one or more acoustic
lenses optionally cover a sub-array, an array, or a group of arrays,
either partially or fully, for example to adjust the acoustic beam
dimensions.

[0169] Each US transducer array and/or sub-array is optionally used to
acquire ultrasonic information regarding a certain line, a surface, or a
volume within the subject's body.

[0170] An array or sub-array optionally scans a surface or a volume
electronically and/or mechanically. Said mechanical scanning may be
performed, for example, by swinging, rotating, or oscillating the array,
the sub-array, or even a group of transducers within the array or
sub-array. In some cases, scanning is optionally electronic in a first
axis and mechanical in a second axis.

[0171] Data acquisition is optionally performed over a short period of
time. Alternatively, data acquisition is performed several times over a
longer period of time, thereby providing time-dependent information.

[0172] In some embodiments, some or all of the transducer components 124,
sub-arrays or arrays, are moved with respect to the surface of ultrasound
garment 110, for example so as to enhance data acquisition flexibility.

[0173] In embodiments, transducer components 124, sub-arrays or arrays can
be moved manually, for example, along special railings. In embodiments,
detachable arrays are optionally fixed to multiple fixation points.
Alternatively, motors may be utilized to change the location of the
arrays, for example using rails with cog-wheels.

Location Sensors

[0174] Additionally or alternatively, ultrasound garment 110 includes one
or more location sensors or location sensor arrays 109 designed to
provide data regarding the relative spatial location and/or orientation
of different regions or transducer components 124 of ultrasound garment
110.

[0175] The location sensors or location sensor arrays 109 optionally
utilize one or more of the many locating sensor technologies known in the
art, for example:

[0176] i. In cases where ultrasound garment 110 has
well defined axes allowing folding, whether or not taking the form of
actual axes, the spatial angle between the surfaces on both sides of such
axes is optionally measured by electric sensors comprising, for example,
location sensor arrays 109.

[0179] iv. A plurality of
radio frequency identification (RFID) chips location sensor arrays 109
mounted on ultrasound garment 110 which may optionally transmit to a base
station (not shown).

[0180] As is known in the art, a group of three or more location sensors
109, mounted on a rigid surface, for example an ultrasonic array or a
sub-array; allows accurate estimation of both the location and
orientation of that surface.

[0181] Conversely, if ultrasound garment 110 has known axes with degrees
of freedom, less than three location sensors 109 may be required to fully
estimate the spatial location and orientation of each ultrasonic array or
sub-array.

[0182] As described above, ultrasound transducers 124 are optionally
configured as having combined receiving and transmitting transducers.
However, ultrasound transducers 124 may be configured with separate
receiving and transmitting transducers. The following narration describes
just one of the many configurations of generating signals fed to
transducers 124 and analyzing the received signals.

Single Large Ultrasonic Array

[0183] FIG. 2 is an embodiment of a single large ultrasonic array system
250, which includes ultrasound garment 110.

[0185] As a result of passing signals through a switching matrix 134,
multiple sub-arrays are defined.

[0186] The result comprises M adaptively defined sub-arrays of transducer
124 where each m'th sub-array (m varies between 1 and M) has Nm
receive datasets, and therefore, for example, Nm analog-to-digital
(A/D) converters.

[0187] Ultrasound garment 110 and beam-forming unit 120, which includes
components besides ultrasound garment 110, processing unit 122, and
operator-interface unit 114, may be used in configurations where the
reception and transmission transducers 124 are combined or separate.

[0188] On transmit; the waveform produced by signal generator 132
optionally passes through amplifiers and/or attenuators, as well as phase
shifter and/or true time-delay devices, as shown in the figure by
triangles, and crossed-out circles as noted above.

[0190] On receive; the signal from each receiving transducer component 124
is directed to the appropriate duplexer 140 using a controllable
switching matrix 134, and may be amplified and/or attenuated, and in some
cases undergo phase shifts and/or true-time delays.

[0191] The resulting signal from duplexers 140 enters Unit A 200 through
data lines 178, as seen in detail in FIG. 3. In Unit A 200, 1:Nm
splitters 192 split signals from duplexers 140 (where m is the sub-array
index). For every nm between 1 and Nm, the nm'th output of
each splitter can be further amplified or attenuated to adjust the
sub-array's apodization pattern, and can also be fed through a phase
shifter or a time-delay device. The signals then enter the nm'th
combiner 193.

[0192] The outputs of each combiner 193 are sampled by an A/D converter
190, and transferred to processing unit 122. Some or all of the
amplifiers, attenuators, phase shifters, and true time-delay devices may
be directed by controller 130.

[0193] In embodiments, the amplification/attenuation and/or the phase
shift/time-delay may be performed in two or more stages, located on one
or two sides of duplexers 140 (FIG. 2). Furthermore, both signal
generator 132 and controller 130 or controllers 130 may be managed
(controlled) by operator-interface unit 114 and/or processing unit 122.

[0194] Signals fed to and/or received from ultrasound transducers 124 may
be generated and/or analyzed in a variety of circuit configurations. The
following narration describes just some of the many options for these
circuit configurations.

Exemplary Circuit Configurations

[0195]FIG. 4 is an embodiment of an active phased array system 400, where
an A/D converter 190 is assigned to each transmitting and/or receiving
transducer component 124 or group of transducer components 124. Such an
"active" phased array supports the generation of multiple receive beams
in post-processing, without prior beam definition.

[0196] On transmit, the waveform produced by signal generator 132 passes
through amplifiers and/or attenuators, as well as phase shifters and/or
true time-delay devices, the parameters for all of which may be
controllable by a controller 130. This signal is fed to transmitting
transducer components 124.

[0197] On receive, the received signal may be amplified and/or attenuated,
and may also undergo phase shifts and/or true-time delays. The resulting
signal is sampled by A/D converter 190, and transferred to processing
unit 122. Both signal generator 132 and controller 130 may be managed by
operator-interface unit 114 and/or processing unit 122.

[0198] FIG. 5 is an embodiment of a single sub-array system 500. In some
configurations, the system may include a plurality of such sub-arrays.
However, some or all of the following units may not necessarily be
duplicated: the controller 130, the signal generator 132, the processing
unit 122, and the user-interface unit 114.

[0199] On receive, the signal from each receiving transducer component 124
may be amplified and/or attenuated, and may also undergo phase shifts
and/or true-time delays. The resulting signal for each receiving
transducer component 124 enters a 1:N splitter 194 (N may vary from one
sub-array to another). For every n between 1 and N, the n'th output of
each splitter can be further amplified or attenuated to adjust the
sub-array's apodization pattern, and can also undergo phase shifts and/or
true-time delays. It then enters the n'th combiner.

[0200] The outputs of each combiner 192 are sampled by A/D converter 190,
and transferred to processing unit 122.

[0201] Both signal generator 132 and controller 130 may be managed by
operator-interface unit 114 and/or processing unit 122. In some
embodiments, the amplification/attenuation and/or the phase
shift/time-delay may be performed in two or more stages, located on one
or two sides of the duplexers.

[0202] In all configurations, some arrays or sub-arrays can be used only
for transmitting or only for receiving, in which case duplexers are not
necessary. FIG. 6 is an embodiment of an "active" phased arrays system
600, including a dedicated transmitter 610 and a dedicated receiver 620.

[0204] Each such pair includes a transmitting sub-array 224 and a
receiving sub-array 324, which may, for example, generate opposite
collinear beams. Some or all receiving sub-arrays 324 may also receive
reflected or transmitted signals generated by other sub-arrays (not
shown).

[0205] It should be understood that FIGS. 2-6 optionally include location
and/or orientation sensors 106 and 109, seen in FIG. 1, and respective
processing.

[0206] In embodiments, a down-converter 630 may be added prior to the A/D
converter, subtracting the frequency of the signal carrier provided by
signal generator 132, which may be constant or time dependent.
Alternatively, down-converter 630 may set the center frequency to one of
the signal carrier frequency's harmonics.

[0207] In other embodiments, the measured analog signal may be correlated
to the output of signal generator 132 in which a matched filter 632 is
optionally utilized, so as to provide pulse compression.

[0208] In some embodiments, the gain applied prior to sampling by the A/D
converter may be automatically adjusted based on the measured signal (a
technique called "adaptive gain control"). The gain can also be time
dependent ("time-gain control"), in order to decrease the dynamic range
to be sampled, thus reducing the number of bits required by the A/D.
Furthermore, in certain embodiments, the A/D converter may produce real
samples, whereas in other embodiments complex measurements are made.

[0209] Technologies relating to transducers 124 may include a variety of
technologies other than planar arrays or phased arrays, in which case the
term "sub-array" should be interpreted as an ultrasound source and/or
detector. The term "sub-array" may also indicate a first separate array
in conjunction with a second separate array.

[0210] Processing unit 122 may employ any technology known in the art. In
some cases, it may be PC-based or any other suitable computing platform.
Additionally or alternatively, one or more digital signal processors
(DSPs), application-specific integrated circuits (ASICs) and/or
field-programmable gate array (FPGA) chips may be used. Thus, processing
unit 122 may include hardware components and/or software modules.

[0211] Operator-interface unit 114 controls the other units according to
the operator's requirements. This may be performed either directly or
through processing unit 122.

[0212] Operator-interface unit 114 may also receive status signals from
the other units. In addition, this unit displays the operator selected
information, which can consist of alphanumeric information, measured
quantitative parameters, 2D or 3D anatomic and/or parametric images,
various sections or projections of anatomic and/or parametric images and
the like.

[0213] Images and parameters may be time dependent. Pseudo-colors may be
used to describe functions of different parameters or a combination of
two or more parameters, for example the videointensity may describe one
parameter whereas the hue may describe another. Any display type, for
example a computer monitor or a 3D holographic display, may be used for
that purpose.

[0214] In some embodiments, some or all of the data and/or control cables
may be replaced with wireless communication of various types, using, for
example, Bluetooth of WIFI technology.

Adjustable Transducer Array Garment

[0215] Ultrasound garment 110 optionally uses a garment that includes
ultrasound transducer ports at multiple locations, to which the operator
selectively chooses and hooks up a variable number of transducers.

[0216] The transducer port locations may be predefined, manually
adjustable, or adjustable using a motor. Motorized adjustment may be
performed during an examination, for automatically moving one or more
probes over a surface, scanning a selected volume. Motorized adjustment
may also be performed before or after an examination, or during system
mode transition. Adjustable transducer array garment optionally includes
a location and/or orientation sensor array described above.

[0217] The data obtained at multiple locations are recorded by the
ultrasound imaging system, and then analyzed either online or offline,
using the techniques described herein.

Beam-Forming and Waveforms

[0218] Beam-forming may be described in terms of complex weights assigned
to different transducers 124 of a transmitting and/or receiving
sub-array. The complex weights are implemented, for example, by applying
gain and/or attenuation, phase delays and/or time delays.

[0219] The complex weights may follow any suitable pattern. For example,
the pattern of the gain of the transducer components 124 may follow a
one-dimensional or a two-dimensional Hamming window. In some embodiments,
the phase setting on transmit should be set to provide one or more focal
points. In this context, a focal point is a spatial location at which the
phases of the signals generated by all relevant transmitting transducer
components 124 is equal to a certain constant, for example 0.

[0220] In further embodiments, the phase setting on receive should provide
dynamic focusing, i.e., the phases for each sample (range-gate) are set
so as to assure that the overall time or phase delay along all paths
between the volume corresponding to the current sample and each receiving
transducer component 124 is equal to a certain constant; for example as
described by Angelsen B A J; "Ultrasound Imaging--Waves, Signals and
Signal Processing"; Emantec A S, Trondheim, Norway 2000; I:1.34-1.44.

[0221] The system may utilize any waveform known in the art, including
both pulsed wave (PW) and continuous wave (CW) transmission. In
embodiments, rectangular pulses may be used. Optionally, coded excitation
techniques may be used, such as linear or non-linear frequency
modulation; binary sequences, for example, Barker codes, Allomorphic
forms and complementary sequences; and poly-phase codes; as described by
Skolnik M I; "Radar Handbook"; McGraw-Hill, Boston, Mass. 1990;
10.1-10.39.

[0222] Furthermore, in embodiments, different coded excitation techniques
or approximately orthogonal sequences of the same coded excitation
technique may be fed to different transducer components. This allows, for
example, dynamic focusing and/or dynamic aperture setting on transmit, as
mentioned by Zheng Y, Silverstein S D; "Novel Transmit Aperture for Very
Large Depth of Focus in Medical Ultrasound B-scan"; IEEE Transactions on
Ultrasonics, Ferroelectrics, and Frequency Control 2006; 53:1079-1087.

System Modes

[0223] Numerous configurations of transmission and/or reception transducer
component allocations may be considered for ultrasound garment 110-based
systems. At any given time, P sub-arrays may be assigned to transmit and
Q sub-arrays may be assigned to receive; P and Q are parameters which may
or may not be equal, and can change over time. Some of these sub-arrays
may perform both transmission and reception.

[0224] Furthermore, a certain receiving transducer sub-array may provide
multiple receive datasets; for example, use multiple A/D converters; each
of which can relate to different beam configurations.

[0226] In some embodiments, one or more of the following basic modes,
described hereinbelow, can be supported:

[0227] i. Reflection-based volume imaging.

[0228] ii. Reflection-based UCT.

[0229] iii. Reflection-based UDT.

[0230] iv. Reflection-based beam pairs.

[0231] v. Transmission-based UCT.

[0232] vi. Transmission-based UDT.

[0233] The reflection-based volume imaging and the reflection-based beam
pairs mode are also referred to as the "fundamental reflection modes".

[0234] For each mode, data for the target volume or for parts of that
volume may be obtained once. Alternatively, it may be collected as a
function of time. When time-dependent information is gathered for organs
showing cyclic motion, such as the heart, applicable measurable
biological signals, for example electrocardiography signals, may be
utilized to improve image quality. Such procedures are usually referred
to as gating techniques. For example, the cycle may be divided into K
intervals, and the data for each interval may be integrated over multiple
consecutive cycles.

[0235] In some cases, data may be collected for partial volumes, which may
be defined by the operator or selected automatically following various
criteria. The partial volume covered may also change over time. Data
acquisition for partial volumes usually requires using fewer beams to
cover the scanned volume, and thus allows increased refresh rates, which
are especially useful in applications where the target organ moves over
time, for example cardiac imaging or gastro-intestinal imaging.

[0236] In further embodiments, two or more of the above described imaging
modes, for example reflection-based volume imaging and transmission-based
UCT may be combined, and applied in either concurrent or alternating
fashion. In such cases, the processes for the two or more imaging modes
will be applied.

[0237] Additionally or alternatively, tailored processes may be defined
for these combined modes. For instance, transmission-based measurements,
examples for which are attenuation and time delay measurements, may
provide a reference for various reflection-based processes, performing
operations such as attenuation correction or corrections for speed of
sound variability. Special display configurations may be devised for the
combined modes, providing the operator with various functions or
representations of the information obtained.

[0238] Transmitting and/or receiving a plurality of beams concurrently may
reduce the overall time required to cover the target volume or partial
volume. However, when two or more beams are transmitted at the same time
or approximately at the same time, especially if the beams' main-lobes
cover spatially adjacent volumes, some mutual interference may occur. In
order to prevent such mutual interference, different concurrent beams may
use different transmission frequencies.

[0240] As mentioned hereinabove, reflection modes provide an array of time
dependent echo measurements. Given the approximate local speed of sound,
time dependence may be translated into range dependence. These
measurements are correlated to the local reflection coefficient, but also
are affected by the two-way cumulative attenuation along the beam, up to
the relevant reflecting volume of tissue.

[0241] Conversely, transmission modes usually provide only two scalar
parameters for each beam--an estimate of the speed of sound, and the
total signal attenuation along a beam.

[0242] Furthermore, the beam configuration for reflection and transmission
modes is different. In reflection modes, the transmitting sub-array is
often used for receiving as well. In some cases, additional adjacent
sub-arrays, located on the same side of the subject, are used to receive
the reflected signal as well. In comparison, in transmission modes, one
or more receiving sub-arrays are assigned to each transmitting array. The
transmitting and receiving sub-arrays are located on opposite sides of
the subject.

[0243] In transmission-based UCT, a receive beam should be paired with
each transmit beam. The two beams should be collinear or close to
collinear, and also temporally synchronized.

Reflection-Based Volume Imaging

[0244] This mode is based on acquiring 1D, 2D, or 3D datasets, which may
or may not be time-dependent, by multiple sub-arrays (or arrays). Each
sub-array may be 1D, 2D, or MD, and can scan a target volume using any
scanning pattern. The origin of all beams produced by a sub-array is
referred to as the "phase center" or the "scanning apex". In some cases,
one or more transmitting and/or receiving transducer components may be
included in more than one sub-array. In some embodiments, the system
repetitively scans a plane or a volume at predefined angular directions,
for example equidistant azimuth and/or elevation angles, using one or
more scanning apexes.

[0245] The data acquired by all sub-arrays is compounded to produce one or
more output datasets. In some embodiments, an output dataset may cover
the combined volume of all acquired datasets, thus extending the field of
view. In some further embodiments, only regions covered by several
sub-arrays (or "views"), as determined according to a predefined logic,
are included in the output datasets.

Ultrasound Computed Tomography (UCT)

[0246] The inventor has discovered that ultrasound garments may have
application in UCT and UDT imaging. The following description presents
just some of the many possible means of extracting information to provide
UCT and UDT imaging data.

[0247] Currently available reflection mode or transmission mode UCT
systems usually utilize cylindrical geometry, i.e., the transmitting
and/or receiving sub-arrays are placed on the surface of an approximate
cylinder. Ultrasound garment 110 systems provide a more generalized
geometry, which usually cannot be determined prior to outfitting the
subject with the system.

[0248] In order to solve the new, more complex geometry, the inverse
problem equations may be rewritten and solved. Additionally or
alternatively, one can adjust the scanning and/or signal processing
parameters to obtain samples equivalent to those obtained using, for
example, cylindrical or spherical geometry (this method is referred to
hereinbelow as the "geometry emulation algorithm"). Once these
adjustments are made, any inverse problem method, and especially any UCT
technique, which are known in the art, may be applied. These methods
include, for example, iterative back-projection, filtered
back-projection, and analytic reconstruction; for example as described by
Louis A K; "Medical Imaging: State of the Art and Future Development";
Inverse Problems 1992; 8:709-738.

[0249] The geometry transformation may be performed by introducing phase
and/or time-delays to each transmitting and/or receiving transducer
component, which are set so as to emulate the transmission and/or
reception of the signal from a transducer component placed on the surface
of a pre-selected 3D geometric shape. In an embodiment, this shape is a
cylinder, whose diameter is equal to or greater than the maximal distance
between any pair of sub-arrays (or transmitting/receiving transducer
components). The one-way (transmit or receive) time-delay Δt
required for effectively translating the location of a transmitting
and/or receiving transducer component, whose location with respect to the
center of the current range-gate is {right arrow over (r)}, to a new
location {right arrow over (r)}', given in the same coordinate system,
is:

Δ t = ( r → ' - r → ) c
##EQU00001##

where c is the speed of sound in the medium. Similarly, the one-way phase
delay Δφ is given by:

Δ φ = 2 π mod [ ( r → '
- r → ) λ , 1 ] ##EQU00002##

where λ is the transmitted or received wavelength and `mod` stands
for the modulus operator. If the same transducer component both transmits
and receives, the time-delay and/or phase delay should be doubled.

[0250] The effective location of each transmitting and/or receiving
transducer component may be set according to different criteria. For
example, in reflection mode, for each range-gate, the transducer
component may be effectively placed at the intersection point between the
selected 3D geometric shape and a line connecting its actual location
with the center of the range-gate, as explained below with respect to
FIG. 7. Another solution is translating the effective location of the to
transmitting and/or receiving transducer component to the surface of the
3D geometric shape along a line parallel to the beam's boresight, which
goes through the transducer component's actual location.

Transducer Component Translation

[0251]FIG. 7 shows a configuration of effective transmitting and/or
receiving transducer component translation 700, according to an
embodiment of the present invention. For convenience purposes, a 2D case
is used. The actual surface of ultrasound garment 110 is shown as a black
dashed line, whereas a selected 3D geometric shape 180 is shown as a
black solid line. Arrows 182 show the translation required in this case
for several transducer component locations. Dotted lines connect the
transducer components with the center of the range-gate.

[0252] This transformation requires knowing the actual location and/or
orientation of each transmitting and/or receiving transducer component.
This information may be based on a sensor array, but may also use other
techniques, described in the "Coordinate System Registration" subsection
below. Once this information is available, it may also be used during
reconstruction as a constraint over the solution: there is no reflection
or attenuation outside the actual surface of ultrasound garment 110.

[0253] Additionally or alternatively, dummy `0` measurements may be added
in reflection modes for regions outside the actual surface of ultrasound
garment 110.

[0254] In addition, this transformation changes the effective area of the
sub-array, and may therefore affect beam width (in both axes), angular
resolution, and signal-to-noise ratio (SNR). In some embodiments, the
shape and dimensions of the sub-array may be adjusted to provide more
homogeneous angular resolution and SNR over different beams.

Ultrasound Diffraction Tomography (UDT)

[0255] Unlike UCT, UDT requires that for each transmit beam, multiple
measurements would be made on receive, using a plurality of phase centers
and/or beam directions.

[0256] As in the case of UCT, one may solve the new inverse problem
equations, and/or adjust the system to produce data equivalent to that
obtained in cylindrical geometry platforms (or platforms of other
geometries), using the techniques described in the previous subsection
"Transducer Component Translation".

[0257] Beam configuration design for UDT modes is often quite complex. The
phase center location and orientation of the various receive beams with
respect to the relevant transmit beam may be constant, but it may also
change over spatial location or time. For instance, the spatial angles
formed between the transmit beam and each of the relevant receive beams
may be kept constant. Another possibility is to keep a constant distance
between the phase centers over ultrasound garment 110 surface. Moreover,
in some embodiments, the orientation of the receive beams may adaptively
change during data acquisition per pulse. For example, all receive beams
may be directed at a point along the transmit beam, which is scanned over
time.

Reflection-Based Beam Pairs

[0258] In embodiments, one can obtain additional information by comparing
the reflections measured along opposite collinear beams. Examples for
such additional information, which can be obtained using methods
described hereinbelow, are estimates of the local attenuation
coefficient, or local speed of sound.

[0259] Generating opposite collinear beams in ultrasound garment 110-based
systems, where the data acquisition geometry changes between different
subject 102s and even different examinations, requires precise knowledge
of the relative location and/or orientation of different transducer
components and/or sub-arrays, as well as accurate control over the
scanning apex location, and the directionality of transmit and receive
beams. Methods for evaluating the location and/or orientation of
transducer components and/or sub-arrays are described in the "Coordinate
System Registration" subsection below. These methods also include special
calibration beams, which may be utilized for collinearity optimization.
Various ultrasound garment 110 hardware configurations, as described
hereinabove, can provide adequate control over apex location and beam
directionality.

Applicable Processes

[0260] In various embodiments, one or more of the following processes may
be applied to the acquired data:

[0261] i. Processing per receive
dataset--processing applied directly to each receive dataset, i.e., to
the outputs of each A/D converter.

[0262] ii. Coordinate system
registration--matching the coordinate systems of data acquired by
multiple sub-arrays (or arrays) or by one or more sub-arrays at different
time frames.

[0263] iii. Compounding--combining the data obtained from
multiple sub-arrays or from one or more sub-arrays at different time
frames to form one or more new datasets.

[0264] iv. Further processing
may be applied for display purposes, according to the operator's
requirements.

[0265] Examples of such processes are given in the current section. It
should be emphasized that the use of all these processes is not
restricted to ultrasound garment 110 systems as described herein, but
rather may be expanded to any ultrasound imaging system where data is
acquired at multiple positions and/or tilts, using one or more imaging
probes, and the data from the multiple positions and/or tilts is combined
and compounded to generate one or more datasets, which may be one-, two-,
or three-dimensional, and either time dependent or time independent.

Processing per Receive Dataset

[0266] The processing per receive dataset may use any suitable technique
known in the art. Some processing steps are:

[0267] i. Logarithmic
compression--the magnitude or squared magnitude of the sampled data may
be converted into logarithmic units, for example decibels, in order to
reduce the dynamic range.

[0268] ii. Time-gain control (TGC)--time
(range) dependent gain corrections may be applied. These corrections may
be performed in hardware, software, or a combination thereof. The
parameters of these corrections may be set by the operator, but may also
be automatically determined.

[0269] iii. Dynamic range windowing--mapping
all values to a range between predefined minimal and maximal values.
Values lower than a certain threshold may be set to the minimal value,
whereas values higher than another threshold may be set to the maximal
value.

[0270] iv. Brightness transfer function (BTF)--applying certain
predefined or adjustable functions to the values. These functions are
usually aimed at improving the contrast for specific ranges of signal
level.

Coordinate System Registration

[0271] As mentioned above, registration may be defined as a process
mapping any point in one coordinate system to the corresponding point in
another system. This mapping may be spatial and/or temporal. Ultrasound
garment 110-based systems provide three potential sources for location
and/or orientation information, each of which may provide time dependent
information:

[0272] 1) The sensor array, if included in the system,
provides direct estimates of location and/or orientation for multiple
sub-array or array transducer components. However, the accuracy of these
estimates is fairly limited.

[0273] 2) A higher degree of information
accuracy may be obtained with special beam configurations ("calibration
beams"). In some cases, the calibration beam design may be founded on the
assumption that when a transmit beam and a receive beam are well aligned,
the transmission mode and perhaps the reflection mode signal levels are
expected to be higher than in other, non-aligned scenarios.
Configurations include:

[0274] i) In transmission UCT mode, several
receive beams, having slightly different orientations and/or apexes, may
be used per transmit beam. By selecting the receive beam producing the
highest signal intensity, one can align the receive beam with the
transmit beam. Such measurements can also be performed iteratively,
decreasing the orientation and apex location diversity between
consecutive steps.

[0275] ii) The same technique may be applied to the
transmit beam and the central receive beam in transmission UDT mode,
which are supposed to be collinear.

[0276] iii) Similarly, in
reflection-based volume imaging, the angular location of a second
sub-array's phase center with respect to a first sub-array's phase center
may be estimated as follows: the second sub-array should transmit several
calibration pulses towards the general direction of the first sub-array.
The second sub-array thus "draws a line" over the image acquired by the
first sub-array, which can be detected and directionally analyzed. In
further cases, the calibration beams may utilize the assumption that when
two beams are aligned, the transmitted and/or reflected signal for the
two beams is best matched. Some configurations:

[0277] i) In UCT mode,
one may switch the roles of the transmitting and the receiving
sub-arrays. When the two beams are perfectly aligned, such a switch
should have negligible effect on both the overall attenuation and the
mean speed of sound measured. Some minor mismatch is still expected,
mainly due to noise.

[0278] ii) The same technique may be applied to the
transmit beam and the central receive beam in transmission UDT mode,
which are supposed to be collinear.

[0279] iii) In reflection-based beam
pairs mode, when a pair of beams is precisely aligned, and after flipping
one of the datasets, the range-dependent signal for the overlapping
portion of the beams should be very similar, since the two sensors are
placed on opposite sides of the subject.

[0280] The difference between
the two datasets is expected to primarily result from differences in
cumulative attenuation and time delays along the beams. In order to
minimize the effect of these differences when comparing the two datasets,
one may also apply local pattern recognition techniques or calculate
various functions of local correlation coefficients, rather than simply
calculate the overall correlation between pairs of datasets. In some
embodiments, one or more calibration beams can be transmitted when the
subject is outfitted with ultrasound garment 110, or upon mode
transition. Calibration beams may also be transmitted at certain time
intervals during the ongoing operation of various modes, so as to correct
for location and/or orientation changes over time.

[0281] 3) The acquired
image data, to which software-based registration techniques may be
applied, also providing information regarding the location and/or
orientation of multiple sub-arrays or array transducer components. The
acquired image data is formed directly in reflection-based volume
imaging. Alternatively, acquired image data may be formed in
reflection-based beam pairs mode. In other modes, 2D and/or 3D images
are usually generated by reconstruction techniques applied to data
acquired by multiple sub-arrays. Such reconstruction techniques may also
be utilized in reflection-based beam pairs mode. In these cases, short
bursts of reflection-based volume imaging may be used for coordinate
system registration. Additionally or alternatively, in UCT or UDT modes,
multiple small changes in the orientation and/or location estimate for
every sub-array may be introduced prior to reconstruction, and the
configuration providing the sharpest overall image should be selected.

[0282] In certain embodiments, transducer components having a very high
reflection coefficient ("strong reflectors") may be embedded in known
positions along ultrasound garment 110. Different strong reflectors may
have different shapes or different reflection characteristics, so as to
allow discrimination between them. In reflection-based modes, strong
reflectors should be well visible in the obtained image, assuming the
coverage volume includes ultrasound garment 110's surface. Such strong
reflectors thus provide additional information concerning the relative
position and/or orientation of various transmitting and/or receiving
transducer components or sub-arrays.

[0283] In some embodiments, data provided by two or more of the
abovementioned sources is combined or fused. Data fusion may be performed
using any technique known in the art. For example, if a sensor array is
present and/or calibration beams are transmitted, their measurements may
be used to initialize a software-based registration process. Additionally
or alternatively, linear or non-linear combinations of the different
estimates can be used. For instance, the final estimated location and/or
orientation may be set to the software solution if the difference between
the two estimates is lower than a predefined value. Otherwise, the final
estimated location and/or orientation would be set to the sensor array
(and/or calibration beam) measurement.

Software-Based Registration

[0284] As mentioned hereinabove, the image in UCT and UDT modes is
reconstructed using multiple sub-arrays. Therefore, this subsection
relates especially to the fundamental reflection modes.

[0285] Software-based registration methods may be coarsely divided into
two groups--rigid registration and elastic registration. Rigid
registration assumes that the two or more datasets registered describe a
rigid body, so that only global translation and rotation of the datasets
are required; for example as taught in U.S. Pat. No. 6,159,152; Dec. 12,
2000, by Sumanaweera T S, Pang L, Bolorforosh S S; "Medical Diagnostic
Ultrasound System and Method for Multiple Image Registration". Elastic
registration also allows for local deformation, for example due to soft
tissue deformation, in motion of subject 102 or organ motion, as
described by Krucker J F, LeCarpentier G L, Fowlkes J B, Carson P L;
"Rapid Elastic Image Registration for 3-D Ultrasound"; IEEE Transactions
on Medical Imaging 2002; 21: 1384-1394.

[0286] Each process may utilize one or more similarity measures, for
example, mutual information measures, correlation coefficient on
intensity values or on gradient images, and intensity values using optic
flow hypothesis. In some cases, the registration accuracy may be better
than the spatial resolution, in which case it is referred to as
"sub-pixel resolution" registration. Within this document, the term
"pixel" relates to picture transducer components of 1D, 2D, and 3D
datasets. The term "voxel", sometimes referring to 3D picture transducer
components, is not used.

[0287] In the fundamental reflection modes, for each frame (or
time-frame), the datasets registered are obtained approximately at the
same time. Consequently, one may assume that the 1D, 2D, or 3D images
describe certain regions of a large rigid volume, and thus apply rigid
registration techniques, using, for example, sub-pixel resolution.

[0288] However, since the speed of sound changes from one medium to the
other, the time difference between the pulse generation and the arrival
of the reflected signal, which is used to estimate the reflector's
distance from the US transducer array 110 or sub-array, also depends on
the tissue types along the beam path; and therefore on the beam path
itself. Elastic registration techniques can therefore provide more
accurate or additional information. In some cases, a single registration
step may be applied, which is either rigid or elastic. In other cases,
two registration steps may be used: rigid registration, followed by
elastic registration, which improves overall performance, and can also
provide an input to further data extraction processes.

[0289] In cases where the target organ moves significantly during data
acquisition, the dataset acquired should be time dependent, and temporal
registration should also be employed, for example using
electrocardiography (ECG) gating.

Data Compounding

[0290] Data compounding techniques for both reflection-based and
transmission-based UCT and UDT modes were mentioned in the "System Modes"
section above. The current subsection relates mainly to the fundamental
reflection modes.

Fundamental Techniques

[0291] Once spatially dependent datasets have been obtained by several
sub-arrays for a certain time frame, these "input datasets" may be
compounded to produce one or more "output datasets", each of which
providing information regarding a predefined coordinate grid. These grids
can be Cartesian, but other grid types, for example hexagonal, helical,
or spherical grids, may also be used. The grid of the output datasets may
cover a substantially larger volume than any input dataset grid, thus
providing an extended field of view.

[0292] A possible compounding method can be based on interpolating the
data for each input dataset to the coordinate grid of every output
dataset, and then calculating the weighted mean over all input datasets
per output grid point; in which case only input datasets whose field of
view covers the relevant grid point should be considered.

[0293] Alternatively, interpolation may be performed simultaneously to all
datasets. Any interpolation technique known in the art can be used for
these purposes, for example, linear interpolation, cubic interpolation,
and cubic smoothing spline. As a result of such spatial averaging, the
output dataset is expected to include lower speckle noise and thermal
noise levels. Image contrast may also be improved as a direct result.
Furthermore, given sufficient data, accurate information may be
ascertained for an output grid in which the distance between adjacent
transducer components is smaller than that in the input datasets, so that
the resulting spatial resolution would be superior to that in the input
datasets.

[0294] When interpolation is applied separately to each input dataset, the
averaging weights may be computed according to various criteria. Some
examples:

[0295] i. In ultrasound imaging, each sub-array usually
produces approximately constant axial (range dependent) resolution, but
the lateral (cross-range) resolution may worsen as the distance from the
transducer increases. This is a result of using spherical scanning
configurations; for example beam steering in azimuth and/or elevation. In
addition, when beam steering techniques are used with a constant-size
sub-array, the beam width usually increases with the off-broadside angle.
Therefore, per output grid point, higher weights can be assigned to input
datasets whose near-by pixels provide better lateral resolution.
Alternatively, the weights may increase, for example in inverse
proportion, as the effective volume of the relevant pixels within an
input dataset decreases.

[0296] ii. The local SNR per sample in each
dataset is a function of various parameters, including, inter alia, the
transmission frequency; the distance from the transducer; the beam
steering spatial angle; and the cumulative attenuation along the beam,
which increases with the distance from the transducer. To obtain optimal
results, the averaging weights can also depend on the local SNR estimate
per dataset.

[0297] iii. In some cases, highly absorbent or reflective
regions within a sub-array's coverage area may cause shadowing in the
image, i.e., substantially reduce the signal levels received from scanned
regions located behind them along the relevant ultrasound beams. In order
to cope with this effect, low weights may be assigned to datasets in
which the local signal level is significantly lower than in the other
datasets. A variety of operators may be applied for this purpose. For
example, the signal level may be compared to the local arithmetic or
geometric average over all datasets, the median over all datasets, a
certain percentile of the datasets, or the average over all datasets plus
a certain multiple of the standard deviation over all datasets.

[0298] Overall performance may be enhanced by the following iterative
process:

[0299] i. Calculate an output dataset, according to the
methods described hereinabove.

[0300] ii. Interpolate the output dataset
in order to estimate the values for every grid point of each input
dataset.

[0301] iii. Compare the results to the input datasets, and
update the output dataset accordingly. For example, very large
differences between an input dataset and an interpolated output dataset
may be detected, following a local update of that region within the
output dataset.

[0302] iv. If certain cessation criteria, for example
maximal number of iterations, or negligible changes in the output dataset
over the last iteration, have not been met, return to step ii.

Multi-Frequency Datasets

[0303] As mentioned before, multiple sub-arrays may transmit
simultaneously or approximately simultaneously, using orthogonal or
almost orthogonal waveforms. Scanning each small region within a target
volume by multiple transmission frequencies or waveforms may also be used
to extract additional or improved information.

[0304] One aspect of this matter relates to the fact that, for a given
sub-array configuration, the beam pattern changes with the transmission
waveform. Therefore, highly reflective transducer components in the beam
side-lobes, causing side-lobe clutter (also discussed below), contribute
differently to the samples in different waveforms. Averaging or weighted
averaging over datasets of several different waveforms can thus reduce
clutter effects.

[0305] Another aspect is tissue classification. For each grid point of an
output dataset, various functions of the adjacent input dataset grid
points of different waveforms can be calculated, providing information
regarding tissue type. For example, statistical attributes of the
waveform dependent data, such as standard deviation or maximum to minimum
ratio, can be utilized.

[0306] Inaccuracies in the time-gain control (TGC) process, applied prior
to data compounding, may introduce errors into the measurements for one
or more waveforms, and consequently skew the tissue classification
results.

Attenuation Correction

[0307] Signal attenuation in ultrasound imaging is usually described in
terms of a local attenuation coefficient λ(r,θ,φ) (r,
θ and φ are the three spherical coordinates), whose effect on
reflected echo measurement is cumulative in logarithmic units. The
effective one-way (transmit or receive) energy attenuation factor for a
distance R along a beam whose boresight points at a spatial angle
(θ,φ), is given by:

exp [ - ∫ 0 R λ ( r , θ , φ )
r ] . ##EQU00003##

[0308] When the signal energy is given in logarithmic units, for example
in decibels, the effective one-way energy attenuation factor is

- ∫ 0 R λ ( r , θ , φ ) r
. ##EQU00004##

[0309] The integral is often replaced by summation over discrete values.

[0310] A local attenuation coefficient map may be derived from the outputs
of the transmission-based UCT mode. By activating both this UCT mode and
a reflection-based mode at a certain sequence, for example at
interleaving frames, one may use the UCT-based attenuation map to correct
the reflection-based map. However, this process increases the data
acquisition duration per frame, and thus increases system sensitivity to
motion of the subject and/or the imaged organ.

[0311] In some embodiments of the invention, local attenuation
measurements, which provide important spatially and/or temporally
dependent clinical information, and allow improving ultrasound images by
applying local attenuation correction, may be performed using only
reflection-based information. The following is an explanation of just one
method for providing local attenuation measurements for an ultrasound
garment of the present invention; as well as existing ultrasound imaging
systems. The main concept underlying this method is that elastic
registration between multiple input datasets can provide multiple
logarithmic energy measurements mq (q is the dataset index) for each
small target region, located in all input datasets by registration. Each
of these measurements mq undergoes cumulative attenuation along a
different path {right arrow over (r)}q. Data acquisition geometry is
generally known, so that a set of equations may be written, describing
the relationships between λ(r,θ,φ) values for different
regions. For example, for a single small target region, viewed by two
paths {right arrow over (r)}q1 and {right arrow over (r)}q2:

where (x, y, z) is a Cartesian coordinate system. This equation is
referred to as the "two-path attenuation equation".

[0312] One possible geometry used for solving this problem is based on
pairs of opposite collinear reflection beams, which are also provided by
the reflection-based beam pairs mode. First of all, the data for the two
beams has to be registered to a single coordinate system with an axial
dimension x (ranging between 0 and X), yielding two registered datasets
m1(x) and m2(x). Since the overall side-to-side attenuation,
λtot, should be equal in both datasets, it can be easily shown
that:

where r(x) is the true reflection coefficient along the axial dimension.
These equations, referred to as the "collinear attenuation equations",
are only precise for a noise free environment, but are expected to
provide acceptable results in real scenarios as well.

[0313] In the reflection-based beam pairs mode, elastic registration may
be performed either on pairs of opposite collinear beams or on groups of
adjacent opposite collinear beams. In the first case, the registration is
reduced to a single dimension. As a result, one may look for specific
patterns, which should be located in the two beams, for example maxima or
minima.

[0314] All the located patterns in one beam should be located in the other
one as well, as will be explained with respect to FIG. 8.

[0317] a left to right reflected signal graph 820, meaning that the
reflected ultrasound is measured when looking from left to right; and

[0318] a right to left reflected signal graph 830, as measured when
looking from right to left.

[0319] In graph 810, true reflection peak locations are marked by dashed
lines 812 and 814. Dashed lines 812 and 814 are extended through left to
right reflected signal graph 820 and right to left reflected signal graph
830; in which offsets in peak location are caused by time delays within
the tissue with respect to the nominal speed of sound, whereas peak level
decrease results from cumulative attenuation.

[0320] The signal levels at the locations of the peaks or other detected
patterns, as determined in the left to right reflected signal and in the
right to left reflected signal, may be used to compute the local
attenuation coefficient λ(x) for various intervals of axial
dimension x, using the collinear attenuation equations. One can assume
that the attenuation coefficient λ(x) is homogeneously spread over
regions between adjacent detected peaks or other patterns. This
computation may be repeated for multiple beam pairs, thus providing an
attenuation coefficient map for a 2D or 3D region.

[0321] This process is only applicable if full side-to-side information
has been obtained for all applicable beam pairs. In other cases, one can
generate an attenuation coefficient map for all volumes covered by beam
pairs with full side-to-side coverage, and then iteratively use this map
to complete missing information in beams with partial coverage.

[0322] In another embodiment, the output dataset grid may be divided into
layers taken at incremental ranges. The layers may take any shape, for
example parallel Cartesian layers or dome shaped layers about a
predefined reference point (using spherical coordinates).

[0323] A set of equations similar to the two-path attenuation equation is
optionally written for all output grid points within each layer, assuming
that the attenuation values for the output grid points in all layers
closer to the reference point, have already been determined. For the
first layer, the attenuation within the entire previous layer is assumed
to be 0 [dB]. This "boundary condition" allows the solution of the
equations for all layers.

[0324] The above described processes results in an estimated map of
attenuation coefficients, which is spatially dependent, and in some cases
also time dependent. This map may also be used to correct the map of
reflection coefficients, inherently produced by reflection-based imaging
modes. Combining the two maps, perhaps together with other maps provided
by the system, can aid in the classification of tissue types.
Additionally or alternatively, the complex weights assigned to different
transducers 124 on transmit and/or on receive may be adjusted for each
small scanned volume based on the attenuation coefficient maps, for
example in order to improve focusing on transmit and/or on receive, thus
enhancing spatial resolution.

[0325] The above procedures may take into account the spatially dependent
gain, for example due to time-gain control (TGC), applied prior to the
procedures by the system hardware and software. For that purpose, a local
TGC correction factor may be added to the attenuation coefficient map
obtained, and/or to the samples used as an input to the process.

[0326] In some cases, various additional corrections may be applied to the
sampled data and/or the energy measurements prior to the attenuation
correction process. For example, one may choose to correct for the
two-way range dependent power decay of the spherical ultrasound wave,
which approximately follows the form 1/R4 (where R is the distance
from the transducer). Additionally or alternatively, one can compensate
for beam-shape losses, caused by the fact the energy of the transmit beam
and the gain of the receive beam are not homogeneously distributed over
all spatial angels, or even over all spatial angles within the respective
main-lobes.

[0327] The tissue's local attenuation coefficient may depend on the
transmitted frequency. Therefore, when wideband signals are transmitted,
the process described above may be applied separately to multiple
sub-bands of the received signal. The results for the multiple sub-bands
may then be combined to obtain the final attenuation coefficient
estimation. The received signal may be divided into sub-bands by applying
analog and/or digital filtering to that signal. In some cases, different
sub-bands may also be sampled separately.

Corrections for Speed of Sound Variability

[0328] The average speed of sound in soft tissue is approximately 1540
[m/sec]. However, this speed varies between different tissue types.
During reflection-based image formation, one often assumes a constant
speed of sound, so that the time delay between signal transmission and
the receipt of the reflected signal is linearly correlated to the
distance from the transducer. Variations in speed of sound introduce
positive or negative time delays, making this correlation imprecise.

[0329] The actual local speed of sound may be estimated using the
transmission-based UCT mode. This mode can therefore be activated in some
sequences with a reflection-based mode, for example interleaving frames,
and its output may be used to correct the reflection-based map.

[0330] In some embodiments of the invention, local speed of sound
measurements, which provide important spatially and/or temporally
dependent clinical information and allow improving ultrasound images by
applying local time delay correction, may be performed using only
reflection-based information. The following is an explanation of just one
method for providing local attenuation measurements for an ultrasound
garment of the present invention; as well as existing ultrasound imaging
systems. This method is based on the fact that elastic registration
between multiple input datasets can provide multiple translation
measurement {right arrow over (t)}q (q is the dataset index) for
each small target region with respect to a selected reference input
dataset. These translations are indicative of relative time delays. As
with signal attenuation, signal time delay is also cumulative along each
beam path {right arrow over (r)}q. Data acquisition geometry is
generally known, so that a set of equations may be written, describing
the relationships between {right arrow over (t)}q values for
different regions. For example, for a single small target region, viewed
by two paths {right arrow over (r)}q1 and {right arrow over
(r)}q2:

where c(x,y) is the actual local speed of sound, tq1 and tq2
are the scalar time delays along paths {right arrow over (r)}q1 and
{right arrow over (r)}q2 respectively. This equation is referred to
as the "two-path time-delay equation".

[0331] A possible geometry used for solving this problem is based on pairs
of opposite collinear reflection beams, which can be provided by the
reflection-based beam pairs mode. For each set of beam pairs, one should
look for specific patterns, for example maxima or minima. All the located
patterns in one beam should be located in the other one as well (FIG. 8).
The actual location of the peaks, or other patterns, along the beam pairs
axis is denoted by l(x), and the measured locations along the two
opposite beams are l1(x) and l2(x). The local time delay, given
in units of range, is denoted by d(x). Since the overall side-to-side
time delay, D, should be equal in both datasets, it can be easily shown
that:

[0332] The local speed of sound can be directly extracted from these
equations, referred to as the "collinear time-delay equations", as the
time delay is proportional to the difference between the actual speed of
sound and the nominal speed of sound. While these equations may only be
precise for a noise free environment, they should provide acceptable
results in real scenarios as well.

[0333] The collinear time-delay equations provide measurements of the
local time delay for the locations of the peaks or other patterns
detected. One can assume that the time delay is homogeneously spread over
regions between adjacent detected peaks (or other patterns). This
computation may be repeated for multiple beam pairs, thus providing a
speed of sound map for a 2D or 3D region.

[0334] This process is only applicable if full side-to-side information
has been obtained for all beam pairs. In other cases, one can generate a
speed of sound map for all volumes covered by beam pairs with full
side-to-side coverage, and then use this map to iteratively complete
missing information in beams with partial coverage.

[0335] In a further embodiment, applicable for example to reflection-based
volume imaging, the output dataset grid may be divided into layers taken
at incremental ranges. The layers may take any shape, for example
parallel Cartesian layers, or dome shaped layers about a predefined
reference point (using spherical coordinates).

[0336] A set of equations is optionally written for all output grid points
within each layer, assuming that the speeds of sound for the output grid
points in all layers closer to the reference point have already been
determined. For the first layer, the speed of sound in the previous layer
is assumed to be the nominal speed of sound. This "boundary condition"
allows the solution of the equations for all layers.

[0337] The resulting spatial map of speeds of sound, which in some cases
can also be time dependent, may be used to correct the reflection
coefficient map, inherently produced by reflection-based imaging modes.
It can also be used separately. Moreover, combining the two maps, perhaps
together with other maps provided by the system, can aid in the
classification of tissue types. Additionally or alternatively, the
complex weights assigned to different transducers 124 on transmit and/or
on receive may be adjusted for each small scanned volume based on the
speed of sound maps, for example in order to improve focusing on transmit
and/or on receive, thus enhancing spatial resolution.

[0338] The local speed of sound within the tissue may depend on the
transmitted frequency. Therefore, when wideband signals are transmitted,
the process described above may be applied separately to multiple
sub-bands of the received signal. The results for the multiple sub-bands
may then be combined to obtain the final speed of sound estimation. The
received signal may be divided into sub-bands by applying analog and/or
digital filtering to that signal. In some cases, different sub-bands may
also be sampled separately.

Side-Lobe Clutter Suppression Techniques

[0339] The term "clutter" refers to undesired information that appears in
the imaging plane, obstructing the data of interest. One of the most
common reasons for clutter in ultrasound images is effective imaging of
off-axis objects, lying in a beam's side-lobes. Highly reflective regions
within these side-lobes, for example surfaces between soft and hard
tissues, may produce significant contributions to the measured signal.

[0340] An iterative process may be devised to minimize clutter effects:

[0341] 1) Acquire one or more frames of data for the target volume,
using, for example, an ultrasound garment 110-based system.

[0342] 2) For
each sample (range gate) at each beam position:

[0343] i) Calculate the
beam pattern for the current range, with respect to the applicable
scanning apex, at all other beam positions, normalized so that the peak
value would be 1.0.

[0344] ii) For complex measurements--subtract from
the sample the value at the same range, with respect to the applicable
scanning apex, for all other beam positions, multiplying each value by
the relevant normalized beam pattern value. Alternatively, only beam
positions for which the measurement and/or the normalized beam pattern
value is high are used. The criterion for selecting the beam positions
used for a certain range gate may be, for example, that the measurement
and/or the normalized beam pattern value and/or their multiplication
result exceeds a certain threshold or belongs to the group of B highest
values, where B is a constant. The second method is also applicable to
real measurements.

[0345] iii) Repeat step ii until certain cessation
criteria have been met. This is required because all measurements are
affected by reflectors in all beam positions, so that there are
interdependencies between the samples. The cessation criteria may be as
simple as reaching a certain number of iterations. More complicated
criteria may refer to the average magnitude of changes made in the last
iteration, or the relative average magnitude of changes in the last
several iterations.

[0346] This procedure assumes that the effects of attenuation and
variations in the speed of sound are not severe, so that data from
different beam positions can be compared. This issue can be avoided by
applying attenuation correction techniques and/or time delay corrections
prior to clutter suppression.

[0347] This process requires that for each processed beam, taken at a
spatial angle (θ,φ), information would be available for
θ±Δθ and φ±Δφ, where Δθ
and Δφ are high, for example, higher than 30°, or even
very high, for example higher than 45°.

[0348] The inventor has discovered that some embodiments of present
ultrasound probes cannot provide such an angular coverage, but that such
angular coverage may possibly be achieved in ultrasound garment 110-based
systems. Data acquired by more than one sub-array may result in different
attenuation models for different sub-arrays. The effect of these
differences may be mitigated by applying attenuation correction schemes,
such as those described hereinabove.

Computer Aided Diagnosis Techniques

[0349] Diverse computer aided diagnostic tools may be developed in order
to streamline the diagnostic process and make it quantitative rather than
qualitative. Some clinical applications may also require organ specific
tools. For instance, a software tool may be developed which automatically
detects the fetal skin surface, delineating it from the amniotic fluid.
Based on this surface, various standard imaging views, for example the
sagittal or corona! view of the brain, may be automatically defined by
the software and displayed to the operator. Another example is a tool
designed for evaluating fissure complexity within the fetal brain.

Additional System Modes

Doppler Mode

[0350] The Doppler effect is the most common tool for measuring blood flow
velocities and tissue motion velocities in standard ultrasound imaging
systems. For reflection-based ultrasonic imaging, this effect is
described by the following equation:

f D = 2 fv cos ( θ ) c ##EQU00009##

where f is the transmitted frequency; v is the absolute flow (or motion)
velocity; θ is the angle between the effective directions of the
ultrasonic beam and the flow (or motion) velocity; c is the wave speed;
and fD is the Doppler shift, i.e., the difference between the
frequencies of the observed and the transmitted ultrasound. v
cos(θ) is the radial velocity component, i.e., the velocity's
component along the line of sight from the transducer's phase center to
the target, so that the Doppler shift is directly proportional to the
radial velocity.

[0351] Five types of Doppler modes are usually supported by ultrasound
systems:

[0352] i. CW Doppler studies, which provide the overall radial
velocity spectrum for a specific beam direction. The output usually takes
the form of a two-dimensional graph, where the horizontal axis is the
time index and the vertical axis is the radial velocity, which may either
be positive or negative. The gray-level of each pixel denotes the local
ratio, along a selected direction, between the number of particles moving
at the relevant radial velocity and the total number of particles. Thus,
the outlines of the graph show the maximal velocity as a function of
time.

[0353] ii. PW Doppler studies, which provide the radial velocity
spectrum for a selected depth along a specific angular direction, as a
function of time. The display method is identical to that used in CW
Doppler studies.

[0354] iii. Color flow Doppler imaging, which uses PW,
superimposes a color representation of the dominant radial blood flow
velocity (for each pixel) over a 2D or 3D ultrasonic image, which may or
may not be time dependent.

[0355] 1iv. Tissue Doppler imaging can assess the radial tissue motion
velocity in vascular and cardiac imaging using PW. As in color flow
Doppler imaging, the information is superimposed over the ultrasonic
image.

[0356] v. Power Doppler imaging, which is similar to color flow
Doppler and tissue Doppler imaging. It displays for each pixel the signal
energy for the local dominant Doppler shift. The signal energy is
proportional to the number of particles within the pixel volume which
move at the dominant radial velocity.

[0357] Both CW Doppler studies and PW Doppler studies may be used to
measure either blood flow velocity, for example through a valve or a
blood vessel, or muscle/valve motion velocity, whose peaks are normally
at much lower velocities.

[0358] All the above Doppler modes can be supported by an ultrasound
garment 110-based system. Additional benefits may also be obtained by the
use of multiple sub-arrays. Some applications:

[0359] i. In PW Doppler
studies, a full spectrum for a specific region may be acquired from
multiple directions, thus extending the information provided to the
clinician.

[0360] ii. In CW Doppler studies, which provide range
independent information for a specific direction, one may use two or more
intersecting beams, whose boresight directions may either be constant or
changing over time, to extract spatially dependent data. For example, two
beams may be used, the first pointing in a specific direction, whereas
the second one scans the path of the first beam. If an exceptionally low
or an exceptionally high value is found along the first beam, and is
found again, not necessarily with the same value, for a specific
direction of the second beam, one can assume that the extreme value
corresponds to the intersection point between the first and second beam.

[0361] iii. In color flow Doppler and tissue Doppler imaging, one can
scan a certain volume using two or more sub-arrays, either on receive
only, or both on transmit and on receive. Two or more points of view may
be used to reconstruct for each pixel a 2D projection of the 3D velocity
vector corresponding to the dominant velocity. Three or more points of
view may be used to reconstruct the full 3D velocity vector for each
pixel. This can be performed as follows: The radial velocity measurement
for the i'th point of view, vir, as made using a beam whose
boresight unit vector is {circumflex over
(b)}i=(xi,yi,zi), provides the projection of the
local dominant velocity vector {right arrow over
(v)}=(vx,vy,v.sub.z) on {circumflex over (b)}i, i.e.,
{circumflex over (b)}i{right arrow over (v)}. All unit vectors
{circumflex over (b)}i are known, so that the vector {right arrow
over (v)} may be deduced from three measurements:

[0362] where -1 denotes a matrix inversion operator. A
similar process can be applied to obtain only a 2D projection of the
vector.

[0363] Using more points of view than needed allows obtaining a
vector estimate for each group of two or three points of view. Averaging
over the results may provide more accurate results.

[0364] In some cases, one can limit the volume scanned for Doppler
processing to a specific region, which is either operator defined or
automatically selected. The specific region can be defined based on
anatomic maps, for example by locating blood vessels of interest and
their immediate surroundings. By limiting the scanned is volume, the
number of beam positions required to scan the volume is decreased, so
that the overall refresh rate can be increased. This is important when
significant changes are expected over time, for example in cardiac
imaging.

Moving-Organ Tissue Tracking

[0365] Some organs, for example blood vessels, the cardiac muscle, and the
gastrointestinal system, move over time. One can evaluate this motion in
ultrasound imaging by tracking small localized regions of the image
between consecutive image frames; for example as described by
Ledesma-Carbayo M J, Kybic J, Desco M, et al.; "Spatio-Temporal Nonrigid
Registration for Ultrasound Cardiac Motion Estimation"; IEEE Transactions
on Medical Imaging 2005; 24:1113-1126. This can be done by applying
various elastic registration techniques, for example by optic flow
methods, to datasets obtained at subsequent time frames.

[0366] Such schemes may be utilized by ultrasound garment 110-based
systems. For example, they may be applied to datasets obtained by one or
more sub-arrays and/or to compounded datasets, produced by any imaging
mode. The resulting information can be provided to the operator.

Contrast Imaging

[0367] Several contrast ultrasound imaging methods are known in the art.
In some cases, these methods are tailored to a specific organ. All these
methods are also applicable to ultrasound garment 110-based systems.

Elastography

[0368] In some embodiments, ultrasound garment 110-based systems may
provide elastography features. Any type of internal or external
mechanical stimulus, generated by any source, may be used for that
purpose. For example, a stimulus may be generated by one or more
loudspeakers, one or more transducers 124, and/or one or more apparatuses
comprising a housing with a movable surface, as taught in US Patent
Application 2002/0068870; Jun. 6, 2002 by Alam S K, Feleppa E J, King M,
Lizzi F L; "Hand Held Mechanical Compression Device for Inducing Tissue
Strain".

[0369] The vibration frequency of the source optionally will vary between
1 [Hz] and 100 [kHz].

[0370] The inventor has discovered that the use of multiple sources may
allow producing more localized excitation by means of interference, as
well as improving the control over the directionality of the mechanical
impulse generated.

[0371] Another method for creating a mechanical stimulus, is applying a
constant or time-variable force to the subject's skin surface, or to an
internal organ, during invasive procedures. While a mechanical force is
being applied, either in a cyclic fashion (vibration) or in a non-cyclic
fashion, tissue tracking techniques, for example as described by in the
"Moving Organ Tissue Tracking" subsection, may be applied, producing
estimates of the local tissue motion vectors in response to the
mechanical force. Additionally or alternatively, Doppler-based imaging
modes, as described herein, may be used to estimate the local
time-dependent motion vectors of the tissue. These vectors are indicative
of the tissues' mechanical properties, and may be used for tissue
classification purposes, for example detection of malignant or benign
tumors.

[0372] In a possible configuration, one or more low-frequency sound
sources (LFSSs), such as loudspeakers, are placed either in direct
contact with, or in close proximity to, the subject's skin surface. These
LFSSs, which can be integrated with an ultrasound garment 110-based
system or placed near it, produce directional oscillations within the
imaging target volume. In this configuration, the LFSS carrier frequency
should optionally be lower, by a factor of at least 5, than the highest
pulse repetition frequency used by any sub-array of ultrasound garment
110 system during the elastography mode. This can aid in preventing
smearing of the measured signal, for example, so as to assure that local
tissue motion during the pulse is insignificant.

[0373] The LFSS carrier frequency is typically selected to be low enough
to produce negligible tissue motion during the acquisition of a full
imaging frame, or at least a large sector of such a frame, so that images
can be obtained at multiple phases of a single LFSS oscillation. If that
is not the case, the temporal sampling for each small tissue region is
unsynchronized with the LFSS oscillation, so that one may only be able to
estimate the span or extent of the local tissue motion over multiple
cycles rather than determine the time dependent motion pattern.

Photoacoustic and Thermoacoustic Imaging

[0374] Photoacoustic imaging is a medical imaging modality based on the
photoacoustic effect. Non-ionizing laser pulses are delivered into
biological tissues; some of the delivered energy is converted into heat,
leading to transient thermoelastic expansion and thus ultrasonic
emission. The generated ultrasonic waves are then detected by ultrasonic
transducers to form images. The energy of the ultrasonic emission is
indicative of the local energy deposition, and therefore provides
information regarding the local optical absorption. The energy of the
ultrasonic signals received by the ultrasonic transducers is also
affected by two types of artifacts:

[0375] i. Electromagnetic
phenomena, occurring along the path of the electromagnetic signal.

[0378] When radio-frequency (RF) pulses are used, the technology is
referred to as thermoacoustic imaging rather than photoacoustic imaging.

[0379] Optical absorption and RF absorption are closely associated with
physiological properties. For instance, optical absorption is known to be
related to local hemoglobin concentration and oxygen saturation. Another
exemplary application is visualization of blood vessels, which is based
on the fact that both optical absorption and RF absorption of blood tend
to be high compared to most other tissue types. Generally speaking, the
frequency of the light and/or RF waves used may affect the physiologic
properties observed by photoacoustic or thermoacoustic imaging systems,
as well as their maximal penetration depth, which tends to increase as
the frequency decreases.

[0380] The inventor has discovered that ultrasound garments may have
application in photoacoustic and thermoacoustic imaging. The following
description presents just some of the many possible means of extracting
information to provide photoacoustic and thermoacoustic imaging data.

[0381] In some embodiments, referring back to FIG. 1, one or more sources
of light or RF radiation (jointly referred to hereinbelow as
electromagnetic radiation) may be incorporated into ultrasound garment
110-based systems or placed in close proximity to them. The sources of
light may include, for example, laser relayed by optic fibers. Lenses may
optionally be used to increase the laser beams' coverage area. The RF
sources may include any type of RF-fed antenna known in the art, which
fits the required transmission power and frequency band, for example,
dipole antennas, horn antennas, planar-array antennas, and/or
phased-array antennas.

[0382] The electromagnetic radiation sources may transmit any waveform,
including CW and PW. Optionally, amplitude modulation and/or frequency
modulation may be utilized, as well as coded excitation techniques such
as binary sequences and poly-phase codes. Different electromagnetic
radiation sources may also use different waveforms, thus allowing
simultaneous utilization of several electromagnetic radiation sources.

[0383] In embodiments, the ultrasound transducers 124 and beam-forming
unit 120 should optionally be configured to generate one or more
concurrent receive beams, whose spatial directions may be constant or
time-dependent. The timing of these receive beams may be synchronized to
electromagnetic pulse transmission. Since the speed of sound in tissues
is lower than the speed of light by several orders of magnitude, the time
delay between electromagnetic pulse transmission and ultrasonic signal
reception should be approximately proportional to the distance between
the tissue from which ultrasound waves emanate and the transducers.
Additionally or alternatively, the directions of the receive beams may be
adjusted to match the coverage volume of the electromagnetic radiation
sources.

[0384] Numerous receive beam scanning configurations may be considered.
For example, one of more sub-arrays may be defined, each of which
scanning a plane or a volume. Additionally or alternatively, a plurality
of receive beams may be defined, some of which are parallel and/or
directed at a certain point in space. Another option is using pairs of
opposite collinear beams.

[0385] Processing unit 122 may then apply any reconstruction algorithm
known in the art or described herein. In embodiments, reflection mode
and/or transmission mode UCT algorithms may be applied, with or without
the geometry emulation algorithm. Additionally or alternatively,
attenuation correction techniques and/or corrections for speed of sound
variability, as described hereinabove, may be utilized in order to
minimize the effect of ultrasonic artifacts on local electromagnetic
absorption estimates. The calculations may take into account the one-way
rather than two-way nature of the ultrasonic artifacts in these cases.

[0386] In embodiments, further techniques may be applied to reduce the
effect of electromagnetic artifacts occurring between the electromagnetic
source and the tissue emitting ultrasound waves. For example, a
range-dependent correction factor may be applied. The correction factor
may also take into account the ultrasonic signal as measured for tissues
along the path between the electromagnetic source and the tissue emitting
ultrasound waves.

[0387] In further embodiments, additional information may be obtained by
transmitting more than one type of electromagnetic waveform, for example
more than one transmission frequency.

[0388] Additionally or alternatively, where multiple electromagnetic
radiation sources are used, the ultrasonic data collected using different
electromagnetic radiation sources may be compared and analyzed. For
example, when comparing the ultrasonic data along a line connecting two
electromagnetic radiation sources, as collected by the two said sources,
the collinear time-delay equations may be applied to estimate and
optionally correct the electromagnetic time delays within the tissues.

Therapeutic Systems

High Intensity Focused Ultrasound

[0389] As described hereinabove, HIFU is an ultrasound-based therapeutic
technique. In some embodiments, ultrasound garment 110-based systems can
be used as a source of imaging information, guiding an HIFU apparatus. In
certain embodiments, this imaging information may also include local
temperature estimation at the target region, for controlling HIFU
operation. Local temperature may be evaluated based on the multiple
parameters measured for each point in space as a function of time, for
example local reflection coefficient, local attenuation coefficient, and
local speed of sound. In further embodiments, an array of high intensity
transducers 124 may be integrated with or into ultrasound garment 110.
The radiating transducer components used for HIFU may either be dedicated
to HIFU operation or be used for imaging purposes as well.

[0390] The inventor has discovered that the local measurements of
ultrasound attenuation and/or local speed of sound, made by the processes
provided herein, can be used to adaptively optimize the beam forming
parameters of the high intensity transducer components. As a result, the
focal point can be smaller and more precisely defined, allowing better
control over the target region. Additionally or alternatively, lower
transmitted power levels may be used to obtain the same effect at the
target region, thus improving the system's safety level.

[0391] It is expected that during the life of a patent maturing from this
application many relevant ultrasound garments will be developed, and the
scope of the term ultrasound garment is intended to include all such new
technologies a priori.

[0395] The term "consisting essentially of" means that the composition,
method or structure may include additional ingredients, steps and/or
parts, but only if the additional ingredients, steps and/or parts do not
materially alter the basic and novel characteristics of the claimed
composition, method or structure.

[0396] As used herein, the singular form "a", "an" and "the" include
plural references unless the context clearly dictates otherwise. For
example, the term "a compound" or "at least one compound" may include a
plurality of compounds, including mixtures thereof.

[0397] Throughout this application, various embodiments of this invention
may be presented in a range format. It should be understood that the
description in range format is merely for convenience and brevity and
should not be construed as an inflexible limitation on the scope of the
invention. Accordingly, the description of a range should be considered
to have specifically disclosed all the possible subranges as well as
individual numerical values within that range. For example, description
of a range such as from 1 to 6 should be considered to have specifically
disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2
to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers
within that range, for example, 1, 2, 3, 4, 5, and 6. This applies
regardless of the breadth of the range.

[0398] Whenever a numerical range is indicated herein, it is meant to
include any cited numeral (fractional or integral) within the indicated
range. The phrases "ranging/ranges between" a first indicate number and a
second indicate number and "ranging/ranges from" a first indicate number
"to" a second indicate number are used herein interchangeably and are
meant to include the first and second indicated numbers and all the
fractional and integral numerals therebetween.

[0399] As used herein the term "method" refers to manners, means,
techniques and procedures for accomplishing a given task including, but
not limited to, those manners, means, techniques and procedures either
known to, or readily developed from known manners, means, techniques, and
procedures by practitioners of the mathematical, physical, chemical,
pharmacological, biological, medical, computer sciences, electrical
engineering, mechanical engineering, and biomedical engineering arts.

[0400] As used herein, the term "treating" includes abrogating,
substantially inhibiting, slowing or reversing the progression of a
condition, substantially ameliorating clinical or aesthetical symptoms of
a condition or substantially preventing the appearance of clinical or
aesthetical symptoms of a condition.

[0401] It is appreciated that certain features of the invention, which
are, for clarity, described in the context of separate embodiments, may
also be provided in combination in a single embodiment. Conversely,
various features of the invention, which are, for brevity, described in
the context of a single embodiment, may also be provided separately or in
any suitable subcombination, or as suitable in any other described
embodiment of the invention. Certain features described in the context of
various embodiments are not to be considered essential features of those
embodiments, unless the embodiment is inoperative without those
components.

[0402] In embodiments, some of the algorithms presented herein, such as
the geometry emulation algorithm, and/or their combinations or
sub-combinations, may be utilized on ultrasound garment embodiments as
well as, in some instances, on existing technology.

[0403] Ultrasound garment technology may provide some advantages over
known imaging modalities. Partial comparative analysis between certain
disclosed ultrasound garment configurations and known ultrasound, MRI and
CT systems is provided in the following Appendix A; which together with
the above descriptions illustrate some embodiments of the invention in a
non-limiting fashion.

Appendix A

[0404] The inventor has discovered the following possible analytical
aspects of ultrasound garment systems and presently available ultrasound,
MRI and CT systems. ("fps" stands for "frames per second".)

TABLE-US-00001
US Garment
Systems Ultrasound MRI CT
General Clinical Aspects
Scanned Volume May provide a large 2D plane or small Large 3D volume
3D volume 3D volume
Clinical Data Possibly any plane Limited by possible Any plane or volume
within
Accessibility or volume within transducer the large 3D volume
the large 3D locations and tilts
volume
Refresh Rate May be high for High (~20 fps) for Low (or still) for large
3D volumes
large 3D volumes 3D volumes
General Image Expected to be high Relatively low High
Quality
Inter- and Intra- Expected to be low High Low
Observer Variability
Tissue Classification Generally Not supported Not supported
supported
Imaging for Generally Not supported Not supported
Continuous supported
Monitoring
Exam Location May be bedside Special exam room
Safety No ionizing radiation No ionizing Ionizing radiation
radiation
Contrast agents
often used
Clinical Aspects Specific to Obstetrics and Gynecology
Invasive/Non- May be non- Trans-abdominal Non-invasive
invasive invasive transducers:
non-invasive
Trans-vaginal
transducers:
invasive, limited
imaging views
Additional Clinical Aspects
Image Quality Generally minimal High Minimal
Dependence on
Hardware
Configuration
Cine-loop Acquisition May take Several seconds Several minutes
Duration
Blood Flow Velocity 3D flow vectors Radial component Coarse flow Not
measurable
Measurement generally may be of flow vectors velocity
measured measured measurements

[0405] Although the invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in the
art. Accordingly, it is intended to embrace all such alternatives,
modifications, and variations that fall within the spirit and broad scope
of the appended claims.

[0406] All publications, patents, and patent applications mentioned in
this specification are herein incorporated in their entirety by reference
into the specification, to the same extent as if each individual
publication, patent, or patent application was specifically and
individually indicated to be incorporated herein by reference. In
addition, citation or identification of any reference in this application
shall not be construed as an admission that such reference is available
as prior art to the present invention. To the extent that section
headings are used, they should not be construed as necessarily limiting.